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1231 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Linus Torvalds
|
27bc50fc90 |
- Yu Zhao's Multi-Gen LRU patches are here. They've been under test in
linux-next for a couple of months without, to my knowledge, any negative reports (or any positive ones, come to that). - Also the Maple Tree from Liam R. Howlett. An overlapping range-based tree for vmas. It it apparently slight more efficient in its own right, but is mainly targeted at enabling work to reduce mmap_lock contention. Liam has identified a number of other tree users in the kernel which could be beneficially onverted to mapletrees. Yu Zhao has identified a hard-to-hit but "easy to fix" lockdep splat (https://lkml.kernel.org/r/CAOUHufZabH85CeUN-MEMgL8gJGzJEWUrkiM58JkTbBhh-jew0Q@mail.gmail.com). This has yet to be addressed due to Liam's unfortunately timed vacation. He is now back and we'll get this fixed up. - Dmitry Vyukov introduces KMSAN: the Kernel Memory Sanitizer. It uses clang-generated instrumentation to detect used-unintialized bugs down to the single bit level. KMSAN keeps finding bugs. New ones, as well as the legacy ones. - Yang Shi adds a userspace mechanism (madvise) to induce a collapse of memory into THPs. - Zach O'Keefe has expanded Yang Shi's madvise(MADV_COLLAPSE) to support file/shmem-backed pages. - userfaultfd updates from Axel Rasmussen - zsmalloc cleanups from Alexey Romanov - cleanups from Miaohe Lin: vmscan, hugetlb_cgroup, hugetlb and memory-failure - Huang Ying adds enhancements to NUMA balancing memory tiering mode's page promotion, with a new way of detecting hot pages. - memcg updates from Shakeel Butt: charging optimizations and reduced memory consumption. - memcg cleanups from Kairui Song. - memcg fixes and cleanups from Johannes Weiner. - Vishal Moola provides more folio conversions - Zhang Yi removed ll_rw_block() :( - migration enhancements from Peter Xu - migration error-path bugfixes from Huang Ying - Aneesh Kumar added ability for a device driver to alter the memory tiering promotion paths. For optimizations by PMEM drivers, DRM drivers, etc. - vma merging improvements from Jakub Matěn. - NUMA hinting cleanups from David Hildenbrand. - xu xin added aditional userspace visibility into KSM merging activity. - THP & KSM code consolidation from Qi Zheng. - more folio work from Matthew Wilcox. - KASAN updates from Andrey Konovalov. - DAMON cleanups from Kaixu Xia. - DAMON work from SeongJae Park: fixes, cleanups. - hugetlb sysfs cleanups from Muchun Song. - Mike Kravetz fixes locking issues in hugetlbfs and in hugetlb core. -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQTTMBEPP41GrTpTJgfdBJ7gKXxAjgUCY0HaPgAKCRDdBJ7gKXxA joPjAQDZ5LlRCMWZ1oxLP2NOTp6nm63q9PWcGnmY50FjD/dNlwEAnx7OejCLWGWf bbTuk6U2+TKgJa4X7+pbbejeoqnt5QU= =xfWx -----END PGP SIGNATURE----- Merge tag 'mm-stable-2022-10-08' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Pull MM updates from Andrew Morton: - Yu Zhao's Multi-Gen LRU patches are here. They've been under test in linux-next for a couple of months without, to my knowledge, any negative reports (or any positive ones, come to that). - Also the Maple Tree from Liam Howlett. An overlapping range-based tree for vmas. It it apparently slightly more efficient in its own right, but is mainly targeted at enabling work to reduce mmap_lock contention. Liam has identified a number of other tree users in the kernel which could be beneficially onverted to mapletrees. Yu Zhao has identified a hard-to-hit but "easy to fix" lockdep splat at [1]. This has yet to be addressed due to Liam's unfortunately timed vacation. He is now back and we'll get this fixed up. - Dmitry Vyukov introduces KMSAN: the Kernel Memory Sanitizer. It uses clang-generated instrumentation to detect used-unintialized bugs down to the single bit level. KMSAN keeps finding bugs. New ones, as well as the legacy ones. - Yang Shi adds a userspace mechanism (madvise) to induce a collapse of memory into THPs. - Zach O'Keefe has expanded Yang Shi's madvise(MADV_COLLAPSE) to support file/shmem-backed pages. - userfaultfd updates from Axel Rasmussen - zsmalloc cleanups from Alexey Romanov - cleanups from Miaohe Lin: vmscan, hugetlb_cgroup, hugetlb and memory-failure - Huang Ying adds enhancements to NUMA balancing memory tiering mode's page promotion, with a new way of detecting hot pages. - memcg updates from Shakeel Butt: charging optimizations and reduced memory consumption. - memcg cleanups from Kairui Song. - memcg fixes and cleanups from Johannes Weiner. - Vishal Moola provides more folio conversions - Zhang Yi removed ll_rw_block() :( - migration enhancements from Peter Xu - migration error-path bugfixes from Huang Ying - Aneesh Kumar added ability for a device driver to alter the memory tiering promotion paths. For optimizations by PMEM drivers, DRM drivers, etc. - vma merging improvements from Jakub Matěn. - NUMA hinting cleanups from David Hildenbrand. - xu xin added aditional userspace visibility into KSM merging activity. - THP & KSM code consolidation from Qi Zheng. - more folio work from Matthew Wilcox. - KASAN updates from Andrey Konovalov. - DAMON cleanups from Kaixu Xia. - DAMON work from SeongJae Park: fixes, cleanups. - hugetlb sysfs cleanups from Muchun Song. - Mike Kravetz fixes locking issues in hugetlbfs and in hugetlb core. Link: https://lkml.kernel.org/r/CAOUHufZabH85CeUN-MEMgL8gJGzJEWUrkiM58JkTbBhh-jew0Q@mail.gmail.com [1] * tag 'mm-stable-2022-10-08' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (555 commits) hugetlb: allocate vma lock for all sharable vmas hugetlb: take hugetlb vma_lock when clearing vma_lock->vma pointer hugetlb: fix vma lock handling during split vma and range unmapping mglru: mm/vmscan.c: fix imprecise comments mm/mglru: don't sync disk for each aging cycle mm: memcontrol: drop dead CONFIG_MEMCG_SWAP config symbol mm: memcontrol: use do_memsw_account() in a few more places mm: memcontrol: deprecate swapaccounting=0 mode mm: memcontrol: don't allocate cgroup swap arrays when memcg is disabled mm/secretmem: remove reduntant return value mm/hugetlb: add available_huge_pages() func mm: remove unused inline functions from include/linux/mm_inline.h selftests/vm: add selftest for MADV_COLLAPSE of uffd-minor memory selftests/vm: add file/shmem MADV_COLLAPSE selftest for cleared pmd selftests/vm: add thp collapse shmem testing selftests/vm: add thp collapse file and tmpfs testing selftests/vm: modularize thp collapse memory operations selftests/vm: dedup THP helpers mm/khugepaged: add tracepoint to hpage_collapse_scan_file() mm/madvise: add file and shmem support to MADV_COLLAPSE ... |
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Matthew Wilcox (Oracle)
|
0cd4d02c32 |
sched: use maple tree iterator to walk VMAs
The linked list is slower than walking the VMAs using the maple tree. We can't use the VMA iterator here because it doesn't support moving to an earlier position. Link: https://lkml.kernel.org/r/20220906194824.2110408-49-Liam.Howlett@oracle.com Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Tested-by: Yu Zhao <yuzhao@google.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: David Hildenbrand <david@redhat.com> Cc: David Howells <dhowells@redhat.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: SeongJae Park <sj@kernel.org> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Aneesh Kumar K.V
|
467b171af8 |
mm/demotion: update node_is_toptier to work with memory tiers
With memory tier support we can have memory only NUMA nodes in the top tier from which we want to avoid promotion tracking NUMA faults. Update node_is_toptier to work with memory tiers. All NUMA nodes are by default top tier nodes. With lower(slower) memory tiers added we consider all memory tiers above a memory tier having CPU NUMA nodes as a top memory tier [sj@kernel.org: include missed header file, memory-tiers.h] Link: https://lkml.kernel.org/r/20220820190720.248704-1-sj@kernel.org [akpm@linux-foundation.org: mm/memory.c needs linux/memory-tiers.h] [aneesh.kumar@linux.ibm.com: make toptier_distance inclusive upper bound of toptiers] Link: https://lkml.kernel.org/r/20220830081457.118960-1-aneesh.kumar@linux.ibm.com Link: https://lkml.kernel.org/r/20220818131042.113280-10-aneesh.kumar@linux.ibm.com Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Reviewed-by: "Huang, Ying" <ying.huang@intel.com> Acked-by: Wei Xu <weixugc@google.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Bharata B Rao <bharata@amd.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Hesham Almatary <hesham.almatary@huawei.com> Cc: Jagdish Gediya <jvgediya.oss@gmail.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Tim Chen <tim.c.chen@intel.com> Cc: Yang Shi <shy828301@gmail.com> Cc: SeongJae Park <sj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Vincent Guittot
|
7e9518baed |
sched/fair: Move call to list_last_entry() in detach_tasks
Move the call to list_last_entry() in detach_tasks() after testing loop_max and loop_break. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20220825122726.20819-4-vincent.guittot@linaro.org |
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Vincent Guittot
|
c59862f826 |
sched/fair: Cleanup loop_max and loop_break
sched_nr_migrate_break is set to a fix value and never changes so we can replace it by a define SCHED_NR_MIGRATE_BREAK. Also, we adjust SCHED_NR_MIGRATE_BREAK to be aligned with the init value of sysctl_sched_nr_migrate which can be init to different values. Then, use SCHED_NR_MIGRATE_BREAK to init sysctl_sched_nr_migrate. The behavior stays unchanged unless you modify sysctl_sched_nr_migrate trough debugfs. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20220825122726.20819-3-vincent.guittot@linaro.org |
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Vincent Guittot
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b0defa7ae0 |
sched/fair: Make sure to try to detach at least one movable task
During load balance, we try at most env->loop_max time to move a task. But it can happen that the loop_max LRU tasks (ie tail of the cfs_tasks list) can't be moved to dst_cpu because of affinity. In this case, loop in the list until we found at least one. The maximum of detached tasks remained the same as before. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20220825122726.20819-2-vincent.guittot@linaro.org |
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Huang Ying
|
c959924b0d |
memory tiering: adjust hot threshold automatically
The promotion hot threshold is workload and system configuration dependent. So in this patch, a method to adjust the hot threshold automatically is implemented. The basic idea is to control the number of the candidate promotion pages to match the promotion rate limit. If the hint page fault latency of a page is less than the hot threshold, we will try to promote the page, and the page is called the candidate promotion page. If the number of the candidate promotion pages in the statistics interval is much more than the promotion rate limit, the hot threshold will be decreased to reduce the number of the candidate promotion pages. Otherwise, the hot threshold will be increased to increase the number of the candidate promotion pages. To make the above method works, in each statistics interval, the total number of the pages to check (on which the hint page faults occur) and the hot/cold distribution need to be stable. Because the page tables are scanned linearly in NUMA balancing, but the hot/cold distribution isn't uniform along the address usually, the statistics interval should be larger than the NUMA balancing scan period. So in the patch, the max scan period is used as statistics interval and it works well in our tests. Link: https://lkml.kernel.org/r/20220713083954.34196-4-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Michal Hocko <mhocko@suse.com> Cc: osalvador <osalvador@suse.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@surriel.com> Cc: Shakeel Butt <shakeelb@google.com> Cc: Wei Xu <weixugc@google.com> Cc: Yang Shi <shy828301@gmail.com> Cc: Zhong Jiang <zhongjiang-ali@linux.alibaba.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Huang Ying
|
c6833e1000 |
memory tiering: rate limit NUMA migration throughput
In NUMA balancing memory tiering mode, if there are hot pages in slow memory node and cold pages in fast memory node, we need to promote/demote hot/cold pages between the fast and cold memory nodes. A choice is to promote/demote as fast as possible. But the CPU cycles and memory bandwidth consumed by the high promoting/demoting throughput will hurt the latency of some workload because of accessing inflating and slow memory bandwidth contention. A way to resolve this issue is to restrict the max promoting/demoting throughput. It will take longer to finish the promoting/demoting. But the workload latency will be better. This is implemented in this patch as the page promotion rate limit mechanism. The number of the candidate pages to be promoted to the fast memory node via NUMA balancing is counted, if the count exceeds the limit specified by the users, the NUMA balancing promotion will be stopped until the next second. A new sysctl knob kernel.numa_balancing_promote_rate_limit_MBps is added for the users to specify the limit. Link: https://lkml.kernel.org/r/20220713083954.34196-3-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Michal Hocko <mhocko@suse.com> Cc: osalvador <osalvador@suse.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@surriel.com> Cc: Shakeel Butt <shakeelb@google.com> Cc: Wei Xu <weixugc@google.com> Cc: Yang Shi <shy828301@gmail.com> Cc: Zhong Jiang <zhongjiang-ali@linux.alibaba.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Huang Ying
|
33024536ba |
memory tiering: hot page selection with hint page fault latency
Patch series "memory tiering: hot page selection", v4.
To optimize page placement in a memory tiering system with NUMA balancing,
the hot pages in the slow memory nodes need to be identified.
Essentially, the original NUMA balancing implementation selects the mostly
recently accessed (MRU) pages to promote. But this isn't a perfect
algorithm to identify the hot pages. Because the pages with quite low
access frequency may be accessed eventually given the NUMA balancing page
table scanning period could be quite long (e.g. 60 seconds). So in this
patchset, we implement a new hot page identification algorithm based on
the latency between NUMA balancing page table scanning and hint page
fault. Which is a kind of mostly frequently accessed (MFU) algorithm.
In NUMA balancing memory tiering mode, if there are hot pages in slow
memory node and cold pages in fast memory node, we need to promote/demote
hot/cold pages between the fast and cold memory nodes.
A choice is to promote/demote as fast as possible. But the CPU cycles and
memory bandwidth consumed by the high promoting/demoting throughput will
hurt the latency of some workload because of accessing inflating and slow
memory bandwidth contention.
A way to resolve this issue is to restrict the max promoting/demoting
throughput. It will take longer to finish the promoting/demoting. But
the workload latency will be better. This is implemented in this patchset
as the page promotion rate limit mechanism.
The promotion hot threshold is workload and system configuration
dependent. So in this patchset, a method to adjust the hot threshold
automatically is implemented. The basic idea is to control the number of
the candidate promotion pages to match the promotion rate limit.
We used the pmbench memory accessing benchmark tested the patchset on a
2-socket server system with DRAM and PMEM installed. The test results are
as follows,
pmbench score promote rate
(accesses/s) MB/s
------------- ------------
base 146887704.1 725.6
hot selection 165695601.2 544.0
rate limit 162814569.8 165.2
auto adjustment 170495294.0 136.9
From the results above,
With hot page selection patch [1/3], the pmbench score increases about
12.8%, and promote rate (overhead) decreases about 25.0%, compared with
base kernel.
With rate limit patch [2/3], pmbench score decreases about 1.7%, and
promote rate decreases about 69.6%, compared with hot page selection
patch.
With threshold auto adjustment patch [3/3], pmbench score increases about
4.7%, and promote rate decrease about 17.1%, compared with rate limit
patch.
Baolin helped to test the patchset with MySQL on a machine which contains
1 DRAM node (30G) and 1 PMEM node (126G).
sysbench /usr/share/sysbench/oltp_read_write.lua \
......
--tables=200 \
--table-size=1000000 \
--report-interval=10 \
--threads=16 \
--time=120
The tps can be improved about 5%.
This patch (of 3):
To optimize page placement in a memory tiering system with NUMA balancing,
the hot pages in the slow memory node need to be identified. Essentially,
the original NUMA balancing implementation selects the mostly recently
accessed (MRU) pages to promote. But this isn't a perfect algorithm to
identify the hot pages. Because the pages with quite low access frequency
may be accessed eventually given the NUMA balancing page table scanning
period could be quite long (e.g. 60 seconds). The most frequently
accessed (MFU) algorithm is better.
So, in this patch we implemented a better hot page selection algorithm.
Which is based on NUMA balancing page table scanning and hint page fault
as follows,
- When the page tables of the processes are scanned to change PTE/PMD
to be PROT_NONE, the current time is recorded in struct page as scan
time.
- When the page is accessed, hint page fault will occur. The scan
time is gotten from the struct page. And The hint page fault
latency is defined as
hint page fault time - scan time
The shorter the hint page fault latency of a page is, the higher the
probability of their access frequency to be higher. So the hint page
fault latency is a better estimation of the page hot/cold.
It's hard to find some extra space in struct page to hold the scan time.
Fortunately, we can reuse some bits used by the original NUMA balancing.
NUMA balancing uses some bits in struct page to store the page accessing
CPU and PID (referring to page_cpupid_xchg_last()). Which is used by the
multi-stage node selection algorithm to avoid to migrate pages shared
accessed by the NUMA nodes back and forth. But for pages in the slow
memory node, even if they are shared accessed by multiple NUMA nodes, as
long as the pages are hot, they need to be promoted to the fast memory
node. So the accessing CPU and PID information are unnecessary for the
slow memory pages. We can reuse these bits in struct page to record the
scan time. For the fast memory pages, these bits are used as before.
For the hot threshold, the default value is 1 second, which works well in
our performance test. All pages with hint page fault latency < hot
threshold will be considered hot.
It's hard for users to determine the hot threshold. So we don't provide a
kernel ABI to set it, just provide a debugfs interface for advanced users
to experiment. We will continue to work on a hot threshold automatic
adjustment mechanism.
The downside of the above method is that the response time to the workload
hot spot changing may be much longer. For example,
- A previous cold memory area becomes hot
- The hint page fault will be triggered. But the hint page fault
latency isn't shorter than the hot threshold. So the pages will
not be promoted.
- When the memory area is scanned again, maybe after a scan period,
the hint page fault latency measured will be shorter than the hot
threshold and the pages will be promoted.
To mitigate this, if there are enough free space in the fast memory node,
the hot threshold will not be used, all pages will be promoted upon the
hint page fault for fast response.
Thanks Zhong Jiang reported and tested the fix for a bug when disabling
memory tiering mode dynamically.
Link: https://lkml.kernel.org/r/20220713083954.34196-1-ying.huang@intel.com
Link: https://lkml.kernel.org/r/20220713083954.34196-2-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Wei Xu <weixugc@google.com>
Cc: osalvador <osalvador@suse.de>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Zhong Jiang <zhongjiang-ali@linux.alibaba.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
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Peter Zijlstra
|
0b9d46fc5e |
sched: Rename task_running() to task_on_cpu()
There is some ambiguity about task_running() in that it is unrelated to TASK_RUNNING but instead tests ->on_cpu. As such, rename the thing task_on_cpu(). Suggested-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/Yxhkhn55uHZx+NGl@hirez.programming.kicks-ass.net |
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Abel Wu
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96c1c0cfe4 |
sched/fair: Cleanup for SIS_PROP
The sched-domain of this cpu is only used for some heuristics when SIS_PROP is enabled, and it should be irrelevant whether the local sd_llc is valid or not, since all we care about is target sd_llc if !SIS_PROP. Access the local domain only when there is a need. Signed-off-by: Abel Wu <wuyun.abel@bytedance.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Mel Gorman <mgorman@suse.de> Link: https://lore.kernel.org/r/20220907112000.1854-6-wuyun.abel@bytedance.com |
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Abel Wu
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398ba2b0cc |
sched/fair: Default to false in test_idle_cores()
It's uncertain whether idle cores exist or not if shared sched- domains are not ready, so returning "no idle cores" usually makes sense. While __update_idle_core() is an exception, it checks status of this core and set hint to shared sched-domain if necessary. So the whole logic of this function depends on the existence of shared sched-domain, and can certainly bail out early if it is not available. It's somehow a little tricky, and as Josh suggested that it should be transient while the domain isn't ready. So remove the self-defined default value to make things more clearer. Signed-off-by: Abel Wu <wuyun.abel@bytedance.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Josh Don <joshdon@google.com> Acked-by: Mel Gorman <mgorman@techsingularity.net> Link: https://lore.kernel.org/r/20220907112000.1854-5-wuyun.abel@bytedance.com |
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Abel Wu
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8eeeed9c4a |
sched/fair: Remove useless check in select_idle_core()
The function select_idle_core() only gets called when has_idle_cores is true which can be possible only when sched_smt_present is enabled. This change also aligns select_idle_core() with select_idle_smt() in the way that the caller do the check if necessary. Signed-off-by: Abel Wu <wuyun.abel@bytedance.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Mel Gorman <mgorman@techsingularity.net> Link: https://lore.kernel.org/r/20220907112000.1854-4-wuyun.abel@bytedance.com |
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Abel Wu
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b9bae70440 |
sched/fair: Avoid double search on same cpu
The prev cpu is checked at the beginning of SIS, and it's unlikely to be idle before the second check in select_idle_smt(). So we'd better focus on its SMT siblings. Signed-off-by: Abel Wu <wuyun.abel@bytedance.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Josh Don <joshdon@google.com> Acked-by: Mel Gorman <mgorman@techsingularity.net> Link: https://lore.kernel.org/r/20220907112000.1854-3-wuyun.abel@bytedance.com |
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Abel Wu
|
3e6efe87cd |
sched/fair: Remove redundant check in select_idle_smt()
If two cpus share LLC cache, then the two cores they belong to are also in the same LLC domain. Signed-off-by: Abel Wu <wuyun.abel@bytedance.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Josh Don <joshdon@google.com> Acked-by: Mel Gorman <mgorman@techsingularity.net> Link: https://lore.kernel.org/r/20220907112000.1854-2-wuyun.abel@bytedance.com |
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Ingo Molnar
|
53aa930dc4 |
Merge branch 'sched/warnings' into sched/core, to pick up WARN_ON_ONCE() conversion commit
Merge in the BUG_ON() => WARN_ON_ONCE() conversion commit. Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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Chengming Zhou
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e4fe074d6c |
sched/fair: Don't init util/runnable_avg for !fair task
post_init_entity_util_avg() init task util_avg according to the cpu util_avg at the time of fork, which will decay when switched_to_fair() some time later, we'd better to not set them at all in the case of !fair task. Suggested-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Link: https://lore.kernel.org/r/20220818124805.601-10-zhouchengming@bytedance.com |
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Chengming Zhou
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d6531ab6e5 |
sched/fair: Move task sched_avg attach to enqueue_task_fair()
When wake_up_new_task(), we use post_init_entity_util_avg() to init
util_avg/runnable_avg based on cpu's util_avg at that time, and
attach task sched_avg to cfs_rq.
Since enqueue_task_fair() -> enqueue_entity() -> update_load_avg()
loop will do attach, we can move this work to update_load_avg().
wake_up_new_task(p)
post_init_entity_util_avg(p)
attach_entity_cfs_rq() --> (1)
activate_task(rq, p)
enqueue_task() := enqueue_task_fair()
enqueue_entity() loop
update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH)
if (!se->avg.last_update_time && (flags & DO_ATTACH))
attach_entity_load_avg() --> (2)
This patch move attach from (1) to (2), update related comments too.
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20220818124805.601-9-zhouchengming@bytedance.com
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Chengming Zhou
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df16b71c68 |
sched/fair: Allow changing cgroup of new forked task
commit
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Chengming Zhou
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7e2edaf618 |
sched/fair: Fix another detach on unattached task corner case
commit
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Chengming Zhou
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e1f078f504 |
sched/fair: Combine detach into dequeue when migrating task
When we are migrating task out of the CPU, we can combine detach and
propagation into dequeue_entity() to save the detach_entity_cfs_rq()
in migrate_task_rq_fair().
This optimization is like combining DO_ATTACH in the enqueue_entity()
when migrating task to the CPU. So we don't have to traverse the CFS tree
extra time to do the detach_entity_cfs_rq() -> propagate_entity_cfs_rq(),
which wouldn't be called anymore with this patch's change.
detach_task()
deactivate_task()
dequeue_task_fair()
for_each_sched_entity(se)
dequeue_entity()
update_load_avg() /* (1) */
detach_entity_load_avg()
set_task_cpu()
migrate_task_rq_fair()
detach_entity_cfs_rq() /* (2) */
update_load_avg();
detach_entity_load_avg();
propagate_entity_cfs_rq();
for_each_sched_entity()
update_load_avg()
This patch save the detach_entity_cfs_rq() called in (2) by doing
the detach_entity_load_avg() for a CPU migrating task inside (1)
(the task being the first se in the loop)
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20220818124805.601-6-zhouchengming@bytedance.com
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Chengming Zhou
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859f206290 |
sched/fair: Update comments in enqueue/dequeue_entity()
When reading the sched_avg related code, I found the comments in enqueue/dequeue_entity() are not updated with the current code. We don't add/subtract entity's runnable_avg from cfs_rq->runnable_avg during enqueue/dequeue_entity(), those are done only for attach/detach. This patch updates the comments to reflect the current code working. Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Vincent Guittot <vincent.guittot@linaro.org> Link: https://lore.kernel.org/r/20220818124805.601-5-zhouchengming@bytedance.com |
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Chengming Zhou
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5d6da83c44 |
sched/fair: Reset sched_avg last_update_time before set_task_rq()
set_task_rq() -> set_task_rq_fair() will try to synchronize the blocked task's sched_avg when migrate, which is not needed for already detached task. task_change_group_fair() will detached the task sched_avg from prev cfs_rq first, so reset sched_avg last_update_time before set_task_rq() to avoid that. Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Link: https://lore.kernel.org/r/20220818124805.601-4-zhouchengming@bytedance.com |
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Chengming Zhou
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39c4261191 |
sched/fair: Remove redundant cpu_cgrp_subsys->fork()
We use cpu_cgrp_subsys->fork() to set task group for the new fair task
in cgroup_post_fork().
Since commit
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Chengming Zhou
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78b6b15770 |
sched/fair: Maintain task se depth in set_task_rq()
Previously we only maintain task se depth in task_move_group_fair(), if a !fair task change task group, its se depth will not be updated, so commit |
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Ingo Molnar
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09348d75a6 |
sched/all: Change all BUG_ON() instances in the scheduler to WARN_ON_ONCE()
There's no good reason to crash a user's system with a BUG_ON(), chances are high that they'll never even see the crash message on Xorg, and it won't make it into the syslog either. By using a WARN_ON_ONCE() we at least give the user a chance to report any bugs triggered here - instead of getting silent hangs. None of these WARN_ON_ONCE()s are supposed to trigger, ever - so we ignore cases where a NULL check is done via a BUG_ON() and we let a NULL pointer through after a WARN_ON_ONCE(). There's one exception: WARN_ON_ONCE() arguments with side-effects, such as locking - in this case we use the return value of the WARN_ON_ONCE(), such as in: - BUG_ON(!lock_task_sighand(p, &flags)); + if (WARN_ON_ONCE(!lock_task_sighand(p, &flags))) + return; Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/YvSsKcAXISmshtHo@gmail.com |
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Bing Huang
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18c31c9711 |
sched/fair: Make per-cpu cpumasks static
The load_balance_mask and select_rq_mask percpu variables are only used in kernel/sched/fair.c. Make them static and move their allocation into init_sched_fair_class(). Replace kzalloc_node() with zalloc_cpumask_var_node() to get rid of the CONFIG_CPUMASK_OFFSTACK #ifdef and to align with per-cpu cpumask allocation for RT (local_cpu_mask in init_sched_rt_class()) and DL class (local_cpu_mask_dl in init_sched_dl_class()). [ mingo: Tidied up changelog & touched up the code. ] Signed-off-by: Bing Huang <huangbing@kylinos.cn> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Link: https://lore.kernel.org/r/20220722213609.3901-1-huangbing775@126.com |
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Hao Jia
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d985ee9f44 |
sched/fair: Remove unused parameter idle of _nohz_idle_balance()
After commit
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Dietmar Eggemann
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740cf8a760 |
sched/core: Introduce sched_asym_cpucap_active()
Create an inline helper for conditional code to be only executed on asymmetric CPU capacity systems. This makes these (currently ~10 and future) conditions a lot more readable. Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20220729111305.1275158-2-dietmar.eggemann@arm.com |
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Vincent Guittot
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c82a69629c |
sched/fair: fix case with reduced capacity CPU
The capacity of the CPU available for CFS tasks can be reduced because of other activities running on the latter. In such case, it's worth trying to move CFS tasks on a CPU with more available capacity. The rework of the load balance has filtered the case when the CPU is classified to be fully busy but its capacity is reduced. Check if CPU's capacity is reduced while gathering load balance statistic and classify it group_misfit_task instead of group_fully_busy so we can try to move the load on another CPU. Reported-by: David Chen <david.chen@nutanix.com> Reported-by: Zhang Qiao <zhangqiao22@huawei.com> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: David Chen <david.chen@nutanix.com> Tested-by: Zhang Qiao <zhangqiao22@huawei.com> Link: https://lkml.kernel.org/r/20220708154401.21411-1-vincent.guittot@linaro.org |
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Vincent Donnefort
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b812fc9768 |
sched/fair: Remove the energy margin in feec()
find_energy_efficient_cpu() integrates a margin to protect tasks from bouncing back and forth from a CPU to another. This margin is set as being 6% of the total current energy estimated on the system. This however does not work for two reasons: 1. The energy estimation is not a good absolute value: compute_energy() used in feec() is a good estimation for task placement as it allows to compare the energy with and without a task. The computed delta will give a good overview of the cost for a certain task placement. It, however, doesn't work as an absolute estimation for the total energy of the system. First it adds the contribution to idle CPUs into the energy, second it mixes util_avg with util_est values. util_avg contains the near history for a CPU usage, it doesn't tell at all what the current utilization is. A system that has been quite busy in the near past will hold a very high energy and then a high margin preventing any task migration to a lower capacity CPU, wasting energy. It even creates a negative feedback loop: by holding the tasks on a less efficient CPU, the margin contributes in keeping the energy high. 2. The margin handicaps small tasks: On a system where the workload is composed mostly of small tasks (which is often the case on Android), the overall energy will be high enough to create a margin none of those tasks can cross. On a Pixel4, a small utilization of 5% on all the CPUs creates a global estimated energy of 140 joules, as per the Energy Model declaration of that same device. This means, after applying the 6% margin that any migration must save more than 8 joules to happen. No task with a utilization lower than 40 would then be able to migrate away from the biggest CPU of the system. The 6% of the overall system energy was brought by the following patch: ( |
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Vincent Donnefort
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3e8c6c9aac |
sched/fair: Remove task_util from effective utilization in feec()
The energy estimation in find_energy_efficient_cpu() (feec()) relies on
the computation of the effective utilization for each CPU of a perf domain
(PD). This effective utilization is then used as an estimation of the busy
time for this pd. The function effective_cpu_util() which gives this value,
scales the utilization relative to IRQ pressure on the CPU to take into
account that the IRQ time is hidden from the task clock. The IRQ scaling is
as follow:
effective_cpu_util = irq + (cpu_cap - irq)/cpu_cap * util
Where util is the sum of CFS/RT/DL utilization, cpu_cap the capacity of
the CPU and irq the IRQ avg time.
If now we take as an example a task placement which doesn't raise the OPP
on the candidate CPU, we can write the energy delta as:
delta = OPPcost/cpu_cap * (effective_cpu_util(cpu_util + task_util) -
effective_cpu_util(cpu_util))
= OPPcost/cpu_cap * (cpu_cap - irq)/cpu_cap * task_util
We end-up with an energy delta depending on the IRQ avg time, which is a
problem: first the time spent on IRQs by a CPU has no effect on the
additional energy that would be consumed by a task. Second, we don't want
to favour a CPU with a higher IRQ avg time value.
Nonetheless, we need to take the IRQ avg time into account. If a task
placement raises the PD's frequency, it will increase the energy cost for
the entire time where the CPU is busy. A solution is to only use
effective_cpu_util() with the CPU contribution part. The task contribution
is added separately and scaled according to prev_cpu's IRQ time.
No change for the FREQUENCY_UTIL component of the energy estimation. We
still want to get the actual frequency that would be selected after the
task placement.
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Lukasz Luba <lukasz.luba@arm.com>
Link: https://lkml.kernel.org/r/20220621090414.433602-7-vdonnefort@google.com
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Dietmar Eggemann
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9b340131a4 |
sched/fair: Use the same cpumask per-PD throughout find_energy_efficient_cpu()
The Perf Domain (PD) cpumask (struct em_perf_domain.cpus) stays invariant after Energy Model creation, i.e. it is not updated after CPU hotplug operations. That's why the PD mask is used in conjunction with the cpu_online_mask (or Sched Domain cpumask). Thereby the cpu_online_mask is fetched multiple times (in compute_energy()) during a run-queue selection for a task. cpu_online_mask may change during this time which can lead to wrong energy calculations. To be able to avoid this, use the select_rq_mask per-cpu cpumask to create a cpumask out of PD cpumask and cpu_online_mask and pass it through the function calls of the EAS run-queue selection path. The PD cpumask for max_spare_cap_cpu/compute_prev_delta selection (find_energy_efficient_cpu()) is now ANDed not only with the SD mask but also with the cpu_online_mask. This is fine since this cpumask has to be in syc with the one used for energy computation (compute_energy()). An exclusive cpuset setup with at least one asymmetric CPU capacity island (hence the additional AND with the SD cpumask) is the obvious exception here. Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Tested-by: Lukasz Luba <lukasz.luba@arm.com> Link: https://lkml.kernel.org/r/20220621090414.433602-6-vdonnefort@google.com |
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Dietmar Eggemann
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ec4fc801a0 |
sched/fair: Rename select_idle_mask to select_rq_mask
On 21/06/2022 11:04, Vincent Donnefort wrote:
> From: Dietmar Eggemann <dietmar.eggemann@arm.com>
https://lkml.kernel.org/r/202206221253.ZVyGQvPX-lkp@intel.com discovered
that this patch doesn't build anymore (on tip sched/core or linux-next)
because of commit
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Dietmar Eggemann
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bb44799949 |
sched, drivers: Remove max param from effective_cpu_util()/sched_cpu_util()
effective_cpu_util() already has a `int cpu' parameter which allows to retrieve the CPU capacity scale factor (or maximum CPU capacity) inside this function via an arch_scale_cpu_capacity(cpu). A lot of code calling effective_cpu_util() (or the shim sched_cpu_util()) needs the maximum CPU capacity, i.e. it will call arch_scale_cpu_capacity() already. But not having to pass it into effective_cpu_util() will make the EAS wake-up code easier, especially when the maximum CPU capacity reduced by the thermal pressure is passed through the EAS wake-up functions. Due to the asymmetric CPU capacity support of arm/arm64 architectures, arch_scale_cpu_capacity(int cpu) is a per-CPU variable read access via per_cpu(cpu_scale, cpu) on such a system. On all other architectures it is a a compile-time constant (SCHED_CAPACITY_SCALE). Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Vincent Guittot <vincent.guittot@linaro.org> Tested-by: Lukasz Luba <lukasz.luba@arm.com> Link: https://lkml.kernel.org/r/20220621090414.433602-4-vdonnefort@google.com |
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Vincent Donnefort
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e2f3e35f1f |
sched/fair: Decay task PELT values during wakeup migration
Before being migrated to a new CPU, a task sees its PELT values synchronized with rq last_update_time. Once done, that same task will also have its sched_avg last_update_time reset. This means the time between the migration and the last clock update will not be accounted for in util_avg and a discontinuity will appear. This issue is amplified by the PELT clock scaling. It takes currently one tick after the CPU being idle to let clock_pelt catching up clock_task. This is especially problematic for asymmetric CPU capacity systems which need stable util_avg signals for task placement and energy estimation. Ideally, this problem would be solved by updating the runqueue clocks before the migration. But that would require taking the runqueue lock which is quite expensive [1]. Instead estimate the missing time and update the task util_avg with that value. To that end, we need sched_clock_cpu() but it is a costly function. Limit the usage to the case where the source CPU is idle as we know this is when the clock is having the biggest risk of being outdated. See comment in migrate_se_pelt_lag() for more details about how the PELT value is estimated. Notice though this estimation doesn't take into account IRQ and Paravirt time. [1] https://lkml.kernel.org/r/20190709115759.10451-1-chris.redpath@arm.com Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com> Signed-off-by: Vincent Donnefort <vdonnefort@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Tested-by: Lukasz Luba <lukasz.luba@arm.com> Link: https://lkml.kernel.org/r/20220621090414.433602-3-vdonnefort@google.com |
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Vincent Donnefort
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d05b43059d |
sched/fair: Provide u64 read for 32-bits arch helper
Introducing macro helpers u64_u32_{store,load}() to factorize lockless
accesses to u64 variables for 32-bits architectures.
Users are for now cfs_rq.min_vruntime and sched_avg.last_update_time. To
accommodate the later where the copy lies outside of the structure
(cfs_rq.last_udpate_time_copy instead of sched_avg.last_update_time_copy),
use the _copy() version of those helpers.
Those new helpers encapsulate smp_rmb() and smp_wmb() synchronization and
therefore, have a small penalty for 32-bits machines in set_task_rq_fair()
and init_cfs_rq().
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Lukasz Luba <lukasz.luba@arm.com>
Link: https://lkml.kernel.org/r/20220621090414.433602-2-vdonnefort@google.com
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Chen Yu
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70fb5ccf2e |
sched/fair: Introduce SIS_UTIL to search idle CPU based on sum of util_avg
[Problem Statement]
select_idle_cpu() might spend too much time searching for an idle CPU,
when the system is overloaded.
The following histogram is the time spent in select_idle_cpu(),
when running 224 instances of netperf on a system with 112 CPUs
per LLC domain:
@usecs:
[0] 533 | |
[1] 5495 | |
[2, 4) 12008 | |
[4, 8) 239252 | |
[8, 16) 4041924 |@@@@@@@@@@@@@@ |
[16, 32) 12357398 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ |
[32, 64) 14820255 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@|
[64, 128) 13047682 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ |
[128, 256) 8235013 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@ |
[256, 512) 4507667 |@@@@@@@@@@@@@@@ |
[512, 1K) 2600472 |@@@@@@@@@ |
[1K, 2K) 927912 |@@@ |
[2K, 4K) 218720 | |
[4K, 8K) 98161 | |
[8K, 16K) 37722 | |
[16K, 32K) 6715 | |
[32K, 64K) 477 | |
[64K, 128K) 7 | |
netperf latency usecs:
=======
case load Lat_99th std%
TCP_RR thread-224 257.39 ( 0.21)
The time spent in select_idle_cpu() is visible to netperf and might have a negative
impact.
[Symptom analysis]
The patch [1] from Mel Gorman has been applied to track the efficiency
of select_idle_sibling. Copy the indicators here:
SIS Search Efficiency(se_eff%):
A ratio expressed as a percentage of runqueues scanned versus
idle CPUs found. A 100% efficiency indicates that the target,
prev or recent CPU of a task was idle at wakeup. The lower the
efficiency, the more runqueues were scanned before an idle CPU
was found.
SIS Domain Search Efficiency(dom_eff%):
Similar, except only for the slower SIS
patch.
SIS Fast Success Rate(fast_rate%):
Percentage of SIS that used target, prev or
recent CPUs.
SIS Success rate(success_rate%):
Percentage of scans that found an idle CPU.
The test is based on Aubrey's schedtests tool, including netperf, hackbench,
schbench and tbench.
Test on vanilla kernel:
schedstat_parse.py -f netperf_vanilla.log
case load se_eff% dom_eff% fast_rate% success_rate%
TCP_RR 28 threads 99.978 18.535 99.995 100.000
TCP_RR 56 threads 99.397 5.671 99.964 100.000
TCP_RR 84 threads 21.721 6.818 73.632 100.000
TCP_RR 112 threads 12.500 5.533 59.000 100.000
TCP_RR 140 threads 8.524 4.535 49.020 100.000
TCP_RR 168 threads 6.438 3.945 40.309 99.999
TCP_RR 196 threads 5.397 3.718 32.320 99.982
TCP_RR 224 threads 4.874 3.661 25.775 99.767
UDP_RR 28 threads 99.988 17.704 99.997 100.000
UDP_RR 56 threads 99.528 5.977 99.970 100.000
UDP_RR 84 threads 24.219 6.992 76.479 100.000
UDP_RR 112 threads 13.907 5.706 62.538 100.000
UDP_RR 140 threads 9.408 4.699 52.519 100.000
UDP_RR 168 threads 7.095 4.077 44.352 100.000
UDP_RR 196 threads 5.757 3.775 35.764 99.991
UDP_RR 224 threads 5.124 3.704 28.748 99.860
schedstat_parse.py -f schbench_vanilla.log
(each group has 28 tasks)
case load se_eff% dom_eff% fast_rate% success_rate%
normal 1 mthread 99.152 6.400 99.941 100.000
normal 2 mthreads 97.844 4.003 99.908 100.000
normal 3 mthreads 96.395 2.118 99.917 99.998
normal 4 mthreads 55.288 1.451 98.615 99.804
normal 5 mthreads 7.004 1.870 45.597 61.036
normal 6 mthreads 3.354 1.346 20.777 34.230
normal 7 mthreads 2.183 1.028 11.257 21.055
normal 8 mthreads 1.653 0.825 7.849 15.549
schedstat_parse.py -f hackbench_vanilla.log
(each group has 28 tasks)
case load se_eff% dom_eff% fast_rate% success_rate%
process-pipe 1 group 99.991 7.692 99.999 100.000
process-pipe 2 groups 99.934 4.615 99.997 100.000
process-pipe 3 groups 99.597 3.198 99.987 100.000
process-pipe 4 groups 98.378 2.464 99.958 100.000
process-pipe 5 groups 27.474 3.653 89.811 99.800
process-pipe 6 groups 20.201 4.098 82.763 99.570
process-pipe 7 groups 16.423 4.156 77.398 99.316
process-pipe 8 groups 13.165 3.920 72.232 98.828
process-sockets 1 group 99.977 5.882 99.999 100.000
process-sockets 2 groups 99.927 5.505 99.996 100.000
process-sockets 3 groups 99.397 3.250 99.980 100.000
process-sockets 4 groups 79.680 4.258 98.864 99.998
process-sockets 5 groups 7.673 2.503 63.659 92.115
process-sockets 6 groups 4.642 1.584 58.946 88.048
process-sockets 7 groups 3.493 1.379 49.816 81.164
process-sockets 8 groups 3.015 1.407 40.845 75.500
threads-pipe 1 group 99.997 0.000 100.000 100.000
threads-pipe 2 groups 99.894 2.932 99.997 100.000
threads-pipe 3 groups 99.611 4.117 99.983 100.000
threads-pipe 4 groups 97.703 2.624 99.937 100.000
threads-pipe 5 groups 22.919 3.623 87.150 99.764
threads-pipe 6 groups 18.016 4.038 80.491 99.557
threads-pipe 7 groups 14.663 3.991 75.239 99.247
threads-pipe 8 groups 12.242 3.808 70.651 98.644
threads-sockets 1 group 99.990 6.667 99.999 100.000
threads-sockets 2 groups 99.940 5.114 99.997 100.000
threads-sockets 3 groups 99.469 4.115 99.977 100.000
threads-sockets 4 groups 87.528 4.038 99.400 100.000
threads-sockets 5 groups 6.942 2.398 59.244 88.337
threads-sockets 6 groups 4.359 1.954 49.448 87.860
threads-sockets 7 groups 2.845 1.345 41.198 77.102
threads-sockets 8 groups 2.871 1.404 38.512 74.312
schedstat_parse.py -f tbench_vanilla.log
case load se_eff% dom_eff% fast_rate% success_rate%
loopback 28 threads 99.976 18.369 99.995 100.000
loopback 56 threads 99.222 7.799 99.934 100.000
loopback 84 threads 19.723 6.819 70.215 100.000
loopback 112 threads 11.283 5.371 55.371 99.999
loopback 140 threads 0.000 0.000 0.000 0.000
loopback 168 threads 0.000 0.000 0.000 0.000
loopback 196 threads 0.000 0.000 0.000 0.000
loopback 224 threads 0.000 0.000 0.000 0.000
According to the test above, if the system becomes busy, the
SIS Search Efficiency(se_eff%) drops significantly. Although some
benchmarks would finally find an idle CPU(success_rate% = 100%), it is
doubtful whether it is worth it to search the whole LLC domain.
[Proposal]
It would be ideal to have a crystal ball to answer this question:
How many CPUs must a wakeup path walk down, before it can find an idle
CPU? Many potential metrics could be used to predict the number.
One candidate is the sum of util_avg in this LLC domain. The benefit
of choosing util_avg is that it is a metric of accumulated historic
activity, which seems to be smoother than instantaneous metrics
(such as rq->nr_running). Besides, choosing the sum of util_avg
would help predict the load of the LLC domain more precisely, because
SIS_PROP uses one CPU's idle time to estimate the total LLC domain idle
time.
In summary, the lower the util_avg is, the more select_idle_cpu()
should scan for idle CPU, and vice versa. When the sum of util_avg
in this LLC domain hits 85% or above, the scan stops. The reason to
choose 85% as the threshold is that this is the imbalance_pct(117)
when a LLC sched group is overloaded.
Introduce the quadratic function:
y = SCHED_CAPACITY_SCALE - p * x^2
and y'= y / SCHED_CAPACITY_SCALE
x is the ratio of sum_util compared to the CPU capacity:
x = sum_util / (llc_weight * SCHED_CAPACITY_SCALE)
y' is the ratio of CPUs to be scanned in the LLC domain,
and the number of CPUs to scan is calculated by:
nr_scan = llc_weight * y'
Choosing quadratic function is because:
[1] Compared to the linear function, it scans more aggressively when the
sum_util is low.
[2] Compared to the exponential function, it is easier to calculate.
[3] It seems that there is no accurate mapping between the sum of util_avg
and the number of CPUs to be scanned. Use heuristic scan for now.
For a platform with 112 CPUs per LLC, the number of CPUs to scan is:
sum_util% 0 5 15 25 35 45 55 65 75 85 86 ...
scan_nr 112 111 108 102 93 81 65 47 25 1 0 ...
For a platform with 16 CPUs per LLC, the number of CPUs to scan is:
sum_util% 0 5 15 25 35 45 55 65 75 85 86 ...
scan_nr 16 15 15 14 13 11 9 6 3 0 0 ...
Furthermore, to minimize the overhead of calculating the metrics in
select_idle_cpu(), borrow the statistics from periodic load balance.
As mentioned by Abel, on a platform with 112 CPUs per LLC, the
sum_util calculated by periodic load balance after 112 ms would
decay to about 0.5 * 0.5 * 0.5 * 0.7 = 8.75%, thus bringing a delay
in reflecting the latest utilization. But it is a trade-off.
Checking the util_avg in newidle load balance would be more frequent,
but it brings overhead - multiple CPUs write/read the per-LLC shared
variable and introduces cache contention. Tim also mentioned that,
it is allowed to be non-optimal in terms of scheduling for the
short-term variations, but if there is a long-term trend in the load
behavior, the scheduler can adjust for that.
When SIS_UTIL is enabled, the select_idle_cpu() uses the nr_scan
calculated by SIS_UTIL instead of the one from SIS_PROP. As Peter and
Mel suggested, SIS_UTIL should be enabled by default.
This patch is based on the util_avg, which is very sensitive to the
CPU frequency invariance. There is an issue that, when the max frequency
has been clamp, the util_avg would decay insanely fast when
the CPU is idle. Commit
|
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Zhang Qiao
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fb95a5a04d |
sched/fair: Remove redundant word " *"
" *" is redundant. so remove it. Signed-off-by: Zhang Qiao <zhangqiao22@huawei.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20220617181151.29980-2-zhangqiao22@huawei.com |
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Josh Don
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792b9f65a5 |
sched: Allow newidle balancing to bail out of load_balance
While doing newidle load balancing, it is possible for new tasks to arrive, such as with pending wakeups. newidle_balance() already accounts for this by exiting the sched_domain load_balance() iteration if it detects these cases. This is very important for minimizing wakeup latency. However, if we are already in load_balance(), we may stay there for a while before returning back to newidle_balance(). This is most exacerbated if we enter a 'goto redo' loop in the LBF_ALL_PINNED case. A very straightforward workaround to this is to adjust should_we_balance() to bail out if we're doing a CPU_NEWLY_IDLE balance and new tasks are detected. This was tested with the following reproduction: - two threads that take turns sleeping and waking each other up are affined to two cores - a large number of threads with 100% utilization are pinned to all other cores Without this patch, wakeup latency was ~120us for the pair of threads, almost entirely spent in load_balance(). With this patch, wakeup latency is ~6us. Signed-off-by: Josh Don <joshdon@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20220609025515.2086253-1-joshdon@google.com |
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Chengming Zhou
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51bf903b64 |
sched/fair: Optimize and simplify rq leaf_cfs_rq_list
We notice the rq leaf_cfs_rq_list has two problems when do bugfix backports and some test profiling. 1. cfs_rqs under throttled subtree could be added to the list, and make their fully decayed ancestors on the list, even though not needed. 2. #1 also make the leaf_cfs_rq_list management complex and error prone, this is the list of related bugfix so far: commit |
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K Prateek Nayak
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f5b2eeb499 |
sched/fair: Consider CPU affinity when allowing NUMA imbalance in find_idlest_group()
In the case of systems containing multiple LLCs per socket, like AMD Zen systems, users want to spread bandwidth hungry applications across multiple LLCs. Stream is one such representative workload where the best performance is obtained by limiting one stream thread per LLC. To ensure this, users are known to pin the tasks to a specify a subset of the CPUs consisting of one CPU per LLC while running such bandwidth hungry tasks. Suppose we kickstart a multi-threaded task like stream with 8 threads using taskset or numactl to run on a subset of CPUs on a 2 socket Zen3 server where each socket contains 128 CPUs (0-63,128-191 in one socket, 64-127,192-255 in another socket) Eg: numactl -C 0,16,32,48,64,80,96,112 ./stream8 Here each CPU in the list is from a different LLC and 4 of those LLCs are on one socket, while the other 4 are on another socket. Ideally we would prefer that each stream thread runs on a different CPU from the allowed list of CPUs. However, the current heuristics in find_idlest_group() do not allow this during the initial placement. Suppose the first socket (0-63,128-191) is our local group from which we are kickstarting the stream tasks. The first four stream threads will be placed in this socket. When it comes to placing the 5th thread, all the allowed CPUs are from the local group (0,16,32,48) would have been taken. However, the current scheduler code simply checks if the number of tasks in the local group is fewer than the allowed numa-imbalance threshold. This threshold was previously 25% of the NUMA domain span (in this case threshold = 32) but after the v6 of Mel's patchset "Adjust NUMA imbalance for multiple LLCs", got merged in sched-tip, Commit: |
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Mel Gorman
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cb29a5c19d |
sched/numa: Apply imbalance limitations consistently
The imbalance limitations are applied inconsistently at fork time and at runtime. At fork, a new task can remain local until there are too many running tasks even if the degree of imbalance is larger than NUMA_IMBALANCE_MIN which is different to runtime. Secondly, the imbalance figure used during load balancing is different to the one used at NUMA placement. Load balancing uses the number of tasks that must move to restore imbalance where as NUMA balancing uses the total imbalance. In combination, it is possible for a parallel workload that uses a small number of CPUs without applying scheduler policies to have very variable run-to-run performance. [lkp@intel.com: Fix build breakage for arc-allyesconfig] Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: K Prateek Nayak <kprateek.nayak@amd.com> Link: https://lore.kernel.org/r/20220520103519.1863-4-mgorman@techsingularity.net |
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Mel Gorman
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13ede33150 |
sched/numa: Do not swap tasks between nodes when spare capacity is available
If a destination node has spare capacity but there is an imbalance then two tasks are selected for swapping. If the tasks have no numa group or are within the same NUMA group, it's simply shuffling tasks around without having any impact on the compute imbalance. Instead, it's just punishing one task to help another. Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: K Prateek Nayak <kprateek.nayak@amd.com> Link: https://lore.kernel.org/r/20220520103519.1863-3-mgorman@techsingularity.net |
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Mel Gorman
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70ce3ea9aa |
sched/numa: Initialise numa_migrate_retry
On clone, numa_migrate_retry is inherited from the parent which means that the first NUMA placement of a task is non-deterministic. This affects when load balancing recognises numa tasks and whether to migrate "regular", "remote" or "all" tasks between NUMA scheduler domains. Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: K Prateek Nayak <kprateek.nayak@amd.com> Link: https://lore.kernel.org/r/20220520103519.1863-2-mgorman@techsingularity.net |
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Linus Torvalds
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1ec6574a3c |
This set of changes updates init and user mode helper tasks to be
ordinary user mode tasks. In commit |
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Linus Torvalds
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44d35720c9 |
sysctl changes for v5.19-rc1
For two kernel releases now kernel/sysctl.c has been being cleaned up slowly, since the tables were grossly long, sprinkled with tons of #ifdefs and all this caused merge conflicts with one susbystem or another. This tree was put together to help try to avoid conflicts with these cleanups going on different trees at time. So nothing exciting on this pull request, just cleanups. I actually had this sysctl-next tree up since v5.18 but I missed sending a pull request for it on time during the last merge window. And so these changes have been being soaking up on sysctl-next and so linux-next for a while. The last change was merged May 4th. Most of the compile issues were reported by 0day and fixed. To help avoid a conflict with bpf folks at Daniel Borkmann's request I merged bpf-next/pr/bpf-sysctl into sysctl-next to get the effor which moves the BPF sysctls from kernel/sysctl.c to BPF core. Possible merge conflicts and known resolutions as per linux-next: bfp: https://lkml.kernel.org/r/20220414112812.652190b5@canb.auug.org.au rcu: https://lkml.kernel.org/r/20220420153746.4790d532@canb.auug.org.au powerpc: https://lkml.kernel.org/r/20220520154055.7f964b76@canb.auug.org.au -----BEGIN PGP SIGNATURE----- iQJGBAABCgAwFiEENnNq2KuOejlQLZofziMdCjCSiKcFAmKOq8ASHG1jZ3JvZkBr ZXJuZWwub3JnAAoJEM4jHQowkoinDAkQAJVo5YVM9f74UwYp4PQhTpjxJBCjRoZD z1u9bp5rMj2ujTC8Fr7VmzKaHrb8+r1C1WvCvZtIzemYNB4lZUrHpVDYfXuXiPRB ihPmEjhlPO5PFBx6cVCpI3cu9bEhG00rLc1QXnABx/pXwNPcOTJAGZJVamZvqubk chjgZrb7N+adHPfvS55v1+zpwdeKfpp5U3zuu5qlT/nn0GS0HCVzOj5fj4oC4wtJ IqfUubo+FX50Ga58yQABWNrjaPD9Crykz5ohVazy3ElQl0hJ4VsK65ct3blqc2vz 1Bb8kPpWuv6aZ5nr1lCVE8qvF4ZIL33ySvpg5BSdWLQEDrBbSpzvJe9Yn7wgR+eq y7fhpO24+zRM82EoDMEvyxX9u1n1RsvoXRtf3ds9BGf63MUxk8a1cgjlU6vuyO2U JhDmfM1xzdKvPoY4COOnHzcAiIqzItTqKd09N5y0cahmYstROU8lvp9huhTAHqk1 SjQMbLIZG7OnX8ZeQcR1EB8sq/IOPZT48ejj0iJmQ8FyMaep71MOQLYyLPAq4lgh JHXm8P6QdB57jfJbqAeNSyZoK0qdxOUR/83Zcah7Jjns6vkju1DNatEsaEEI2y2M 4n7/rkHeZ3TyFHBUX4e9FomKvGLsAalDBRiqsuxLSOPMU8rGrNLAslOAtKwvp90X 4ht3M2VP098l =btwh -----END PGP SIGNATURE----- Merge tag 'sysctl-5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux Pull sysctl updates from Luis Chamberlain: "For two kernel releases now kernel/sysctl.c has been being cleaned up slowly, since the tables were grossly long, sprinkled with tons of #ifdefs and all this caused merge conflicts with one susbystem or another. This tree was put together to help try to avoid conflicts with these cleanups going on different trees at time. So nothing exciting on this pull request, just cleanups. Thanks a lot to the Uniontech and Huawei folks for doing some of this nasty work" * tag 'sysctl-5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux: (28 commits) sched: Fix build warning without CONFIG_SYSCTL reboot: Fix build warning without CONFIG_SYSCTL kernel/kexec_core: move kexec_core sysctls into its own file sysctl: minor cleanup in new_dir() ftrace: fix building with SYSCTL=y but DYNAMIC_FTRACE=n fs/proc: Introduce list_for_each_table_entry for proc sysctl mm: fix unused variable kernel warning when SYSCTL=n latencytop: move sysctl to its own file ftrace: fix building with SYSCTL=n but DYNAMIC_FTRACE=y ftrace: Fix build warning ftrace: move sysctl_ftrace_enabled to ftrace.c kernel/do_mount_initrd: move real_root_dev sysctls to its own file kernel/delayacct: move delayacct sysctls to its own file kernel/acct: move acct sysctls to its own file kernel/panic: move panic sysctls to its own file kernel/lockdep: move lockdep sysctls to its own file mm: move page-writeback sysctls to their own file mm: move oom_kill sysctls to their own file kernel/reboot: move reboot sysctls to its own file sched: Move energy_aware sysctls to topology.c ... |
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Eric W. Biederman
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b3f9916d81 |
sched: Update task_tick_numa to ignore tasks without an mm
Qian Cai <quic_qiancai@quicinc.com> wrote: > Reverting the last 3 commits of the series fixed a boot crash. > > |
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Ingo Molnar
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d70522fc54 |
Linux 5.18-rc5
-----BEGIN PGP SIGNATURE----- iQFSBAABCAA8FiEEq68RxlopcLEwq+PEeb4+QwBBGIYFAmJu9FYeHHRvcnZhbGRz QGxpbnV4LWZvdW5kYXRpb24ub3JnAAoJEHm+PkMAQRiGAyEH/16xtJSpLmLwrQzG o+4ToQxSQ+/9UHyu0RTEvHg2THm9/8emtIuYyc/5FgdoWctcSa3AaDcveWmuWmkS KYcdhfJsaEqjNHS3OPYXN84fmo9Hel7263shu5+IYmP/sN0DfQp6UWTryX1q4B3Q 4Pdutkuq63Uwd8nBZ5LXQBumaBrmkkuMgWEdT4+6FOo1mPzwdIGBxCuz1UsNNl5k chLWxkQfe2eqgWbYJrgCQfrVdORXVtoU2fGilZUNrHRVGkkldXkkz5clJfapyZD3 odmZCEbrE4GPKgZwCmDERMfD1hzhZDtYKiHfOQ506szH5ykJjPBcOjHed7dA60eB J3+wdek= =39Ca -----END PGP SIGNATURE----- Merge tag 'v5.18-rc5' into sched/core to pull in fixes & to resolve a conflict - sched/core is on a pretty old -rc1 base - refresh it to include recent fixes. - this also allows up to resolve a (trivial) .mailmap conflict Conflicts: .mailmap Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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Thomas Gleixner
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d664e39912 |
sched: Fix missing prototype warnings
A W=1 build emits more than a dozen missing prototype warnings related to scheduler and scheduler specific includes. Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20220413133024.249118058@linutronix.de |