The patch titled
Use num_possible_cpus() instead of NR_CPUS for timer distribution
has been added to the -mm tree. Its filename is
use-num_possible_cpus-instead-of-nr_cpus-for-timer.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: Use num_possible_cpus() instead of NR_CPUS for timer distribution
From: john stultz <johnstul@xxxxxxxxxx>
To avoid lock contention, we distribute the sched_timer calls across the
cpus so they do not trigger at the same instant. However, I used NR_CPUS,
which can cause needless grouping on small smp systems depending on your
kernel config. This patch converts to using num_possible_cpus() so we
spread it as evenly as possible on every machine.
Briefly tested w/ NR_CPUS=255 and verified reduced contention.
Signed-off-by: John Stultz <johnstul@xxxxxxxxxx>
Acked-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/time/tick-sched.c | 2 +-
1 files changed, 1 insertion(+), 1 deletion(-)
diff -puN kernel/time/tick-sched.c~use-num_possible_cpus-instead-of-nr_cpus-for-timer kernel/time/tick-sched.c
--- a/kernel/time/tick-sched.c~use-num_possible_cpus-instead-of-nr_cpus-for-timer
+++ a/kernel/time/tick-sched.c
@@ -574,7 +574,7 @@ void tick_setup_sched_timer(void)
/* Get the next period (per cpu) */
ts->sched_timer.expires = tick_init_jiffy_update();
offset = ktime_to_ns(tick_period) >> 1;
- do_div(offset, NR_CPUS);
+ do_div(offset, num_possible_cpus());
offset *= smp_processor_id();
ts->sched_timer.expires = ktime_add_ns(ts->sched_timer.expires, offset);
_
Patches currently in -mm which might be from johnstul@xxxxxxxxxx are
futex_unlock_pi-hurts-my-brain-and-may-cause.patch
git-acpi.patch
geode-mfgpt-clock-event-device-support.patch
x86_64-hpet-restore-vread.patch
x86_64-restore-restore-nohpet-cmdline.patch
x86_64-prep-idle-loop-for-dynticks.patch
x86_64-enable-high-resolution-timers-and-dynticks.patch
x86_64-dynticks-disable-hpet_id_legsup-hpets.patch
kernel-time-timekeepingc-cleanups.patch
use-num_possible_cpus-instead-of-nr_cpus-for-timer.patch
kernel-time-clocksourcec-use-list_for_each_entry-instead-of-list_for_each.patch
-
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