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| author | Peter Zijlstra <peterz@infradead.org> | 2013-09-27 17:30:03 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2013-09-28 10:04:47 +0200 |
| commit | 75f93fed50c2abadbab6ef546b265f51ca975b27 (patch) | |
| tree | ae531501cb671c948baedb8e07111f8dda2d5036 | |
| parent | 1a338ac32ca630f67df25b4a16436cccc314e997 (diff) | |
| download | op-kernel-dev-75f93fed50c2abadbab6ef546b265f51ca975b27.zip op-kernel-dev-75f93fed50c2abadbab6ef546b265f51ca975b27.tar.gz | |
sched: Revert need_resched() to look at TIF_NEED_RESCHED
Yuanhan reported a serious throughput regression in his pigz
benchmark. Using the ftrace patch I found that several idle
paths need more TLC before we can switch the generic
need_resched() over to preempt_need_resched.
The preemption paths benefit most from preempt_need_resched and
do indeed use it; all other need_resched() users don't really
care that much so reverting need_resched() back to
tif_need_resched() is the simple and safe solution.
Reported-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: lkp@linux.intel.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20130927153003.GF15690@laptop.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | arch/x86/include/asm/preempt.h | 8 | ||||
| -rw-r--r-- | include/asm-generic/preempt.h | 8 | ||||
| -rw-r--r-- | include/linux/sched.h | 5 |
3 files changed, 5 insertions, 16 deletions
diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h index 1de41690..8729723 100644 --- a/arch/x86/include/asm/preempt.h +++ b/arch/x86/include/asm/preempt.h @@ -80,14 +80,6 @@ static __always_inline bool __preempt_count_dec_and_test(void) } /* - * Returns true when we need to resched -- even if we can not. - */ -static __always_inline bool need_resched(void) -{ - return unlikely(test_preempt_need_resched()); -} - -/* * Returns true when we need to resched and can (barring IRQ state). */ static __always_inline bool should_resched(void) diff --git a/include/asm-generic/preempt.h b/include/asm-generic/preempt.h index 5dc14ed..ddf2b42 100644 --- a/include/asm-generic/preempt.h +++ b/include/asm-generic/preempt.h @@ -85,14 +85,6 @@ static __always_inline bool __preempt_count_dec_and_test(void) } /* - * Returns true when we need to resched -- even if we can not. - */ -static __always_inline bool need_resched(void) -{ - return unlikely(test_preempt_need_resched()); -} - -/* * Returns true when we need to resched and can (barring IRQ state). */ static __always_inline bool should_resched(void) diff --git a/include/linux/sched.h b/include/linux/sched.h index b09798b..2ac5285 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2577,6 +2577,11 @@ static inline bool __must_check current_clr_polling_and_test(void) } #endif +static __always_inline bool need_resched(void) +{ + return unlikely(tif_need_resched()); +} + /* * Thread group CPU time accounting. */ |
