linux/kernel
Vincent Guittot 16b0a7a1a0 sched/fair: Ensure tasks spreading in LLC during LB
schbench shows latency increase for 95 percentile above since:
  commit 0b0695f2b3 ("sched/fair: Rework load_balance()")

Align the behavior of the load balancer with the wake up path, which tries
to select an idle CPU which belongs to the LLC for a waking task.

calculate_imbalance() will use nr_running instead of the spare
capacity when CPUs share resources (ie cache) at the domain level. This
will ensure a better spread of tasks on idle CPUs.

Running schbench on a hikey (8cores arm64) shows the problem:

tip/sched/core :
schbench -m 2 -t 4 -s 10000 -c 1000000 -r 10
Latency percentiles (usec)
	50.0th: 33
	75.0th: 45
	90.0th: 51
	95.0th: 4152
	*99.0th: 14288
	99.5th: 14288
	99.9th: 14288
	min=0, max=14276

tip/sched/core + patch :
schbench -m 2 -t 4 -s 10000 -c 1000000 -r 10
Latency percentiles (usec)
	50.0th: 34
	75.0th: 47
	90.0th: 52
	95.0th: 78
	*99.0th: 94
	99.5th: 94
	99.9th: 94
	min=0, max=94

Fixes: 0b0695f2b3 ("sched/fair: Rework load_balance()")
Reported-by: Chris Mason <clm@fb.com>
Suggested-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Rik van Riel <riel@surriel.com>
Tested-by: Rik van Riel <riel@surriel.com>
Link: https://lkml.kernel.org/r/20201102102457.28808-1-vincent.guittot@linaro.org
2020-11-10 18:38:48 +01:00
..
bpf bpf: Fix scalar32_min_max_or bounds tracking 2020-10-08 11:02:53 +02:00
cgroup for-5.9/block-20200802 2020-08-03 11:57:03 -07:00
configs
debug treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
dma dma-pool: Fix an uninitialized variable bug in atomic_pool_expand() 2020-08-27 09:22:56 +02:00
entry * Misc minor cleanups. 2020-10-12 10:51:02 -07:00
events These are the performance events changes for v5.10: 2020-10-12 14:14:35 -07:00
gcov gcov: add support for GCC 10.1 2020-09-11 09:33:54 -07:00
irq Surgery of the MSI interrupt handling to prepare the support of upcoming 2020-10-12 11:40:41 -07:00
kcsan kcsan: Use tracing-safe version of prandom 2020-08-30 21:50:13 -07:00
livepatch livepatch: Make klp_apply_object_relocs static 2020-05-11 00:31:38 +02:00
locking Merge branch 'locking/urgent' into locking/core, to pick up fixes 2020-10-09 08:55:17 +02:00
power notifier: Fix broken error handling pattern 2020-09-01 09:58:03 +02:00
printk Printk changes for 5.9 2020-08-04 22:22:25 -07:00
rcu A small set of updates for debug objects: 2020-10-12 11:21:24 -07:00
sched sched/fair: Ensure tasks spreading in LLC during LB 2020-11-10 18:38:48 +01:00
time These are the locking updates for v5.10: 2020-10-12 13:06:20 -07:00
trace These are the performance events changes for v5.10: 2020-10-12 14:14:35 -07:00
.gitignore
acct.c mmap locking API: convert mmap_sem comments 2020-06-09 09:39:14 -07:00
async.c treewide: Remove uninitialized_var() usage 2020-07-16 12:35:15 -07:00
audit_fsnotify.c fsnotify: create method handle_inode_event() in fsnotify_operations 2020-07-27 23:25:50 +02:00
audit_tree.c \n 2020-08-06 19:29:51 -07:00
audit_watch.c fsnotify: create method handle_inode_event() in fsnotify_operations 2020-07-27 23:25:50 +02:00
audit.c audit/stable-5.9 PR 20200803 2020-08-04 14:20:26 -07:00
audit.h revert: 1320a4052e ("audit: trigger accompanying records when no rules present") 2020-07-29 10:00:36 -04:00
auditfilter.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
auditsc.c audit/stable-5.9 PR 20200803 2020-08-04 14:20:26 -07:00
backtracetest.c treewide: Replace DECLARE_TASKLET() with DECLARE_TASKLET_OLD() 2020-07-30 11:15:58 -07:00
bounds.c
capability.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
compat.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
configs.c
context_tracking.c context_tracking: Ensure that the critical path cannot be instrumented 2020-06-11 15:14:36 +02:00
cpu_pm.c notifier: Fix broken error handling pattern 2020-09-01 09:58:03 +02:00
cpu.c The changes in this cycle are: 2020-06-03 13:06:42 -07:00
crash_core.c kdump: append kernel build-id string to VMCOREINFO 2020-08-12 10:58:01 -07:00
crash_dump.c crash_dump: Remove no longer used saved_max_pfn 2020-04-15 11:21:54 +02:00
cred.c exec: Teach prepare_exec_creds how exec treats uids & gids 2020-05-20 14:44:21 -05:00
delayacct.c
dma.c
elfcore.c
exec_domain.c
exit.c kernel: add a kernel_wait helper 2020-08-12 10:57:59 -07:00
extable.c
fail_function.c
fork.c mm/fork: Pass new vma pointer into copy_page_range() 2020-09-27 11:21:35 -07:00
freezer.c
futex.c futex: Convert to use the preferred 'fallthrough' macro 2020-08-13 21:02:12 +02:00
gen_kheaders.sh kbuild: add variables for compression tools 2020-06-06 23:42:01 +09:00
groups.c mm: remove the pgprot argument to __vmalloc 2020-06-02 10:59:11 -07:00
hung_task.c kernel/hung_task.c: introduce sysctl to print all traces when a hung task is detected 2020-06-08 11:05:56 -07:00
iomem.c
irq_work.c irq_work, smp: Allow irq_work on call_single_queue 2020-05-28 10:54:15 +02:00
jump_label.c jump_label,module: Fix module lifetime for __jump_label_mod_text_reserved() 2020-09-01 09:58:04 +02:00
kallsyms.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c kcov: make some symbols static 2020-08-12 10:58:02 -07:00
kexec_core.c
kexec_elf.c
kexec_file.c Misc fixes and small updates all around the place: 2020-08-15 10:38:03 -07:00
kexec_internal.h
kexec.c
kheaders.c
kmod.c kmod: remove redundant "be an" in the comment 2020-08-12 10:58:01 -07:00
kprobes.c This tree prepares to unify the kretprobe trampoline handler and make 2020-10-12 14:21:15 -07:00
ksysfs.c
kthread.c uaccess: add force_uaccess_{begin,end} helpers 2020-08-12 10:57:59 -07:00
latencytop.c sysctl: pass kernel pointers to ->proc_handler 2020-04-27 02:07:40 -04:00
Makefile static_call: Add inline static call infrastructure 2020-09-01 09:58:04 +02:00
module_signature.c
module_signing.c
module-internal.h
module.c static_call: Add inline static call infrastructure 2020-09-01 09:58:04 +02:00
notifier.c notifier: Fix broken error handling pattern 2020-09-01 09:58:03 +02:00
nsproxy.c nsproxy: support CLONE_NEWTIME with setns() 2020-07-08 11:14:22 +02:00
padata.c padata: fix possible padata_works_lock deadlock 2020-09-04 17:51:55 +10:00
panic.c panic: make print_oops_end_marker() static 2020-08-12 10:58:02 -07:00
params.c
pid_namespace.c pid_namespace: use checkpoint_restore_ns_capable() for ns_last_pid 2020-07-19 20:14:42 +02:00
pid.c cap-checkpoint-restore-v5.9 2020-08-04 15:02:07 -07:00
profile.c
ptrace.c
range.c
reboot.c arch: remove unicore32 port 2020-07-01 12:09:13 +03:00
regset.c regset: kill ->get() 2020-07-27 14:31:12 -04:00
relay.c kernel/relay.c: fix memleak on destroy relay channel 2020-08-21 09:52:53 -07:00
resource.c /dev/mem: Revoke mappings when a driver claims the region 2020-05-27 11:10:05 +02:00
rseq.c
scs.c mm: memcontrol: account kernel stack per node 2020-08-07 11:33:25 -07:00
seccomp.c seccomp: don't leave dangling ->notif if file allocation fails 2020-09-08 11:30:16 -07:00
signal.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
smp.c smp: Fix a potential usage of stale nr_cpus 2020-07-22 10:22:04 +02:00
smpboot.c
smpboot.h
softirq.c softirq: Add debug check to __raise_softirq_irqoff() 2020-09-16 15:18:56 +02:00
stackleak.c stackleak: let stack_erasing_sysctl take a kernel pointer buffer 2020-09-19 13:13:39 -07:00
stacktrace.c stacktrace: Remove reliable argument from arch_stack_walk() callback 2020-09-18 14:24:16 +01:00
static_call.c static_call: Fix return type of static_call_init 2020-10-02 21:18:25 +02:00
stop_machine.c
sys_ni.c all arch: remove system call sys_sysctl 2020-08-14 19:56:56 -07:00
sys.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
sysctl-test.c
sysctl.c mm: allow a controlled amount of unfairness in the page lock 2020-09-17 10:26:41 -07:00
task_work.c task_work: only grab task signal lock when needed 2020-08-13 09:01:38 -06:00
taskstats.c
test_kprobes.c
torture.c torture: Dump ftrace at shutdown only if requested 2020-06-29 12:01:45 -07:00
tracepoint.c tracepoint: Fix out of sync data passing by static caller 2020-10-02 21:18:25 +02:00
tsacct.c
ucount.c ucount: Make sure ucounts in /proc/sys/user don't regress again 2020-04-07 21:51:27 +02:00
uid16.c
uid16.h
umh.c usermodehelper: reset umask to default before executing user process 2020-10-06 10:31:52 -07:00
up.c
user_namespace.c nsproxy: add struct nsset 2020-05-09 13:57:12 +02:00
user-return-notifier.c
user.c user.c: make uidhash_table static 2020-06-04 19:06:24 -07:00
usermode_driver.c umd: Stop using split_argv 2020-07-07 11:58:59 -05:00
utsname_sysctl.c sysctl: pass kernel pointers to ->proc_handler 2020-04-27 02:07:40 -04:00
utsname.c nsproxy: add struct nsset 2020-05-09 13:57:12 +02:00
watch_queue.c watch_queue: Limit the number of watches a user can hold 2020-08-17 09:39:18 -07:00
watchdog_hld.c
watchdog.c kernel/watchdog.c: convert {soft/hard}lockup boot parameters to sysctl aliases 2020-06-08 11:05:56 -07:00
workqueue_internal.h
workqueue.c treewide: Make all debug_obj_descriptors const 2020-09-24 21:56:25 +02:00