vcpu_is_preempted() now can represent the actual state of the VCPU, so the scheduler can make better decisions when it picks the idle CPU to enqueue a task on. I executed a whole bunch of scheduler tests [0]. One particular test that shows the importance of vcpu_is_preempted() is AIO stress-ng test:
x Disabled vcpu_is_preempted() stress-ng: info: [100] stressor bogo ops real time usr time sys time bogo ops/s bogo ops/s stress-ng: info: [100] (secs) (secs) (secs) (real time) (usr+sys time) stress-ng: info: [100] aio 222927 10.01 0.89 27.61 22262.04 7822.00 stress-ng: info: [139] aio 217043 10.01 1.00 26.80 21685.46 7807.30 stress-ng: info: [178] aio 217261 10.01 1.08 26.79 21709.36 7795.51 + Enabled vcpu_is_preempted() stress-ng: info: [100] aio 432750 10.00 1.14 19.03 43264.33 21455.13 stress-ng: info: [139] aio 426771 10.01 1.09 18.67 42629.13 21597.72 stress-ng: info: [179] aio 533039 10.00 1.42 20.39 53281.70 24440.12 Signed-off-by: Sergey Senozhatsky <[email protected]> --- arch/arm64/include/asm/spinlock.h | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/arch/arm64/include/asm/spinlock.h b/arch/arm64/include/asm/spinlock.h index 9083d6992603..6a390eeabe82 100644 --- a/arch/arm64/include/asm/spinlock.h +++ b/arch/arm64/include/asm/spinlock.h @@ -11,17 +11,20 @@ /* See include/linux/spinlock.h */ #define smp_mb__after_spinlock() smp_mb() -/* - * Changing this will break osq_lock() thanks to the call inside - * smp_cond_load_relaxed(). - * - * See: - * https://lore.kernel.org/lkml/[email protected] - */ #define vcpu_is_preempted vcpu_is_preempted + +#ifdef CONFIG_PARAVIRT +extern bool paravirt_vcpu_is_preempted(int cpu); + +static inline bool vcpu_is_preempted(int cpu) +{ + return paravirt_vcpu_is_preempted(cpu); +} +#else static inline bool vcpu_is_preempted(int cpu) { return false; } +#endif /* CONFIG_PARAVIRT */ #endif /* __ASM_SPINLOCK_H */ -- 2.27.0
