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bdaac4902a
linux/mm
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Wu Fengguang bdaac4902a writeback: balanced_rate cannot exceed write bandwidth 
Add an upper limit to balanced_rate according to the below inequality.
This filters out some rare but huge singular points, which at least
enables more readable gnuplot figures.

When there are N dd dirtiers,

	balanced_dirty_ratelimit = write_bw / N

So it holds that

	balanced_dirty_ratelimit <= write_bw

The singular points originate from dirty_rate in the below formular:

        balanced_dirty_ratelimit = task_ratelimit * write_bw / dirty_rate
where
	dirty_rate = (number of page dirties in the past 200ms) / 200ms

In the extreme case, if all dd tasks suddenly get blocked on something
else and hence no pages are dirtied at all, dirty_rate will be 0 and
balanced_dirty_ratelimit will be inf. This could happen in reality.

Note that these huge singular points are not a real threat, since they
are _guaranteed_ to be filtered out by the
	min(balanced_dirty_ratelimit, task_ratelimit)
line in bdi_update_dirty_ratelimit(). task_ratelimit is based on the
number of dirty pages, which will never _suddenly_ fly away like
balanced_dirty_ratelimit. So any weirdly large balanced_dirty_ratelimit
will be cut down to the level of task_ratelimit.

There won't be tiny singular points though, as long as the dirty pages
lie inside the dirty throttling region (above the freerun region).
Because there the dd tasks will be throttled by balanced_dirty_pages()
and won't be able to suddenly dirty much more pages than average.

Acked-by: Jan Kara <jack@suse.cz>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
2011-12-18 14:20:33 +08:00
..
backing-dev.c backing-dev: ensure wakeup_timer is deleted 2011-11-11 13:29:04 +01:00
bootmem.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
bounce.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
cleancache.c mm: cleancache core ops functions and config 2011-05-26 10:01:36 -06:00
compaction.c mm: compaction: make compact_zone_order() static 2011-10-31 17:30:49 -07:00
debug-pagealloc.c debug-pagealloc: add support for highmem pages 2011-10-31 17:30:48 -07:00
dmapool.c mm: fix implicit stat.h usage in dmapool.c 2011-10-31 09:20:12 -04:00
fadvise.c
failslab.c fault-injection: add ability to export fault_attr in arbitrary directory 2011-08-03 14:25:20 -10:00
filemap_xip.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
filemap.c fs: Make write(2) interruptible by a fatal signal 2011-12-02 09:17:05 +08:00
fremap.c mm: delete various needless include <linux/module.h> 2011-10-31 09:20:11 -04:00
highmem.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
huge_memory.c thp: reduce khugepaged freezing latency 2011-12-09 07:50:28 -08:00
hugetlb.c thp: set compound tail page _count to zero 2011-12-09 07:50:28 -08:00
hwpoison-inject.c Fix common misspellings 2011-03-31 11:26:23 -03:00
init-mm.c atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
internal.h mm: thp: tail page refcounting fix 2011-11-02 16:06:57 -07:00
Kconfig memblock: add NO_BOOTMEM config symbol 2011-10-31 17:30:47 -07:00
Kconfig.debug mm: debug-pagealloc: fix kconfig dependency warning 2011-03-22 17:44:02 -07:00
kmemcheck.c
kmemleak-test.c kmemleak: remove memset by using kzalloc 2011-01-27 18:31:51 +00:00
kmemleak.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
ksm.c oom: fix race while temporarily setting current's oom_score_adj 2011-10-31 17:30:45 -07:00
maccess.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
madvise.c fs: kill i_alloc_sem 2011-07-20 20:47:46 -04:00
Makefile Cross Memory Attach 2011-10-31 17:30:44 -07:00
memblock.c mm/memblock.c: quiet sparse noise 2011-10-31 17:30:50 -07:00
memcontrol.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
memory_hotplug.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
memory-failure.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
memory.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
mempolicy.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
mempool.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
migrate.c mm/migrate.c: pair unlock_page() and lock_page() when migrating huge pages 2011-12-09 07:50:28 -08:00
mincore.c mm: clarify the radix_tree exceptional cases 2011-08-03 14:25:24 -10:00
mlock.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
mm_init.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
mmap.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
mmu_context.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
mmu_notifier.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
mmzone.c mm: delete various needless include <linux/module.h> 2011-10-31 09:20:11 -04:00
mprotect.c thp: mprotect: transparent huge page support 2011-01-13 17:32:44 -08:00
mremap.c thp: mremap support and TLB optimization 2011-10-31 17:30:48 -07:00
msync.c sanitize vfs_fsync calling conventions 2010-05-21 18:31:21 -04:00
nobootmem.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
nommu.c xen: map foreign pages for shared rings by updating the PTEs directly 2011-11-16 12:13:08 -05:00
oom_kill.c oom: do not kill tasks with oom_score_adj OOM_SCORE_ADJ_MIN 2011-11-15 22:41:51 -02:00
page_alloc.c mm: Ensure that pfn_valid() is called once per pageblock when reserving pageblocks 2011-12-09 07:50:28 -08:00
page_cgroup.c mm/page_cgroup.c: quiet sparse noise 2011-11-02 16:07:00 -07:00
page_io.c block: kill off REQ_UNPLUG 2011-03-10 08:52:27 +01:00
page_isolation.c mm: page_isolation: codeclean fix comment and rm unneeded val init 2010-10-26 16:52:11 -07:00
page-writeback.c writeback: balanced_rate cannot exceed write bandwidth 2011-12-18 14:20:33 +08:00
pagewalk.c pagewalk: fix code comment for THP 2011-07-25 20:57:09 -07:00
percpu-km.c percpu: clear memory allocated with the km allocator 2010-10-02 10:28:42 +03:00
percpu-vm.c percpu: fix chunk range calculation 2011-11-22 08:09:46 -08:00
percpu.c percpu: explain why per_cpu_ptr_to_phys() is more complicated than necessary 2011-11-23 08:20:53 -08:00
pgtable-generic.c mm/pgtable-generic.c: fix CONFIG_SWAP=n build 2011-01-26 10:49:58 +10:00
prio_tree.c sanitize <linux/prefetch.h> usage 2011-05-20 12:50:29 -07:00
process_vm_access.c Cross Memory Attach 2011-10-31 17:30:44 -07:00
quicklist.c mm: delete various needless include <linux/module.h> 2011-10-31 09:20:11 -04:00
readahead.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
rmap.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
shmem.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
slab.c slab, lockdep: Fix silly bug 2011-12-05 09:44:00 +01:00
slob.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
slub.c slub: avoid potential NULL dereference or corruption 2011-11-24 08:44:19 +02:00
sparse-vmemmap.c mm: delete various needless include <linux/module.h> 2011-10-31 09:20:11 -04:00
sparse.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
swap_state.c mm: delete various needless include <linux/module.h> 2011-10-31 09:20:11 -04:00
swap.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
swapfile.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
thrash.c mm/thrash.c: quiet sparse noise 2011-10-31 17:30:50 -07:00
truncate.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
util.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
vmalloc.c mm: vmalloc: check for page allocation failure before vmlist insertion 2011-12-09 07:50:29 -08:00
vmscan.c vmscan: use atomic-long for shrinker batching 2011-12-09 07:50:27 -08:00
vmstat.c mm/vmstat.c: cache align vm_stat 2011-10-31 17:30:51 -07:00