Messages in this thread Patch in this message | | | Date | Fri, 27 Sep 2013 17:30:03 +0200 | From | Peter Zijlstra <> | Subject | [PATCH] sched: Revert need_resched() to look at TIF_NEED_RESCHED |
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Subject: sched: Revert need_resched() to look at TIF_NEED_RESCHED From: Peter Zijlstra <peterz@infradead.org> Date: Fri Sep 27 17:20:30 CEST 2013
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> --- arch/x86/include/asm/preempt.h | 8 -------- include/asm-generic/preempt.h | 8 -------- include/linux/sched.h | 5 +++++ 3 files changed, 5 insertions(+), 16 deletions(-)
--- a/arch/x86/include/asm/preempt.h +++ b/arch/x86/include/asm/preempt.h @@ -80,14 +80,6 @@ static __always_inline bool __preempt_co } /* - * 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) --- a/include/asm-generic/preempt.h +++ b/include/asm-generic/preempt.h @@ -85,14 +85,6 @@ static __always_inline bool __preempt_co } /* - * 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) --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2577,6 +2577,11 @@ static inline bool __must_check current_ } #endif +static __always_inline bool need_resched(void) +{ + return unlikely(tif_need_resched()); +} + /* * Thread group CPU time accounting. */
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