mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-19 10:44:14 +08:00
75f93fed50
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>
106 lines
2.6 KiB
C
106 lines
2.6 KiB
C
#ifndef __ASM_PREEMPT_H
|
|
#define __ASM_PREEMPT_H
|
|
|
|
#include <linux/thread_info.h>
|
|
|
|
/*
|
|
* We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users
|
|
* that think a non-zero value indicates we cannot preempt.
|
|
*/
|
|
static __always_inline int preempt_count(void)
|
|
{
|
|
return current_thread_info()->preempt_count & ~PREEMPT_NEED_RESCHED;
|
|
}
|
|
|
|
static __always_inline int *preempt_count_ptr(void)
|
|
{
|
|
return ¤t_thread_info()->preempt_count;
|
|
}
|
|
|
|
/*
|
|
* We now loose PREEMPT_NEED_RESCHED and cause an extra reschedule; however the
|
|
* alternative is loosing a reschedule. Better schedule too often -- also this
|
|
* should be a very rare operation.
|
|
*/
|
|
static __always_inline void preempt_count_set(int pc)
|
|
{
|
|
*preempt_count_ptr() = pc;
|
|
}
|
|
|
|
/*
|
|
* must be macros to avoid header recursion hell
|
|
*/
|
|
#define task_preempt_count(p) \
|
|
(task_thread_info(p)->preempt_count & ~PREEMPT_NEED_RESCHED)
|
|
|
|
#define init_task_preempt_count(p) do { \
|
|
task_thread_info(p)->preempt_count = PREEMPT_DISABLED; \
|
|
} while (0)
|
|
|
|
#define init_idle_preempt_count(p, cpu) do { \
|
|
task_thread_info(p)->preempt_count = PREEMPT_ENABLED; \
|
|
} while (0)
|
|
|
|
/*
|
|
* We fold the NEED_RESCHED bit into the preempt count such that
|
|
* preempt_enable() can decrement and test for needing to reschedule with a
|
|
* single instruction.
|
|
*
|
|
* We invert the actual bit, so that when the decrement hits 0 we know we both
|
|
* need to resched (the bit is cleared) and can resched (no preempt count).
|
|
*/
|
|
|
|
static __always_inline void set_preempt_need_resched(void)
|
|
{
|
|
*preempt_count_ptr() &= ~PREEMPT_NEED_RESCHED;
|
|
}
|
|
|
|
static __always_inline void clear_preempt_need_resched(void)
|
|
{
|
|
*preempt_count_ptr() |= PREEMPT_NEED_RESCHED;
|
|
}
|
|
|
|
static __always_inline bool test_preempt_need_resched(void)
|
|
{
|
|
return !(*preempt_count_ptr() & PREEMPT_NEED_RESCHED);
|
|
}
|
|
|
|
/*
|
|
* The various preempt_count add/sub methods
|
|
*/
|
|
|
|
static __always_inline void __preempt_count_add(int val)
|
|
{
|
|
*preempt_count_ptr() += val;
|
|
}
|
|
|
|
static __always_inline void __preempt_count_sub(int val)
|
|
{
|
|
*preempt_count_ptr() -= val;
|
|
}
|
|
|
|
static __always_inline bool __preempt_count_dec_and_test(void)
|
|
{
|
|
return !--*preempt_count_ptr();
|
|
}
|
|
|
|
/*
|
|
* Returns true when we need to resched and can (barring IRQ state).
|
|
*/
|
|
static __always_inline bool should_resched(void)
|
|
{
|
|
return unlikely(!*preempt_count_ptr());
|
|
}
|
|
|
|
#ifdef CONFIG_PREEMPT
|
|
extern asmlinkage void preempt_schedule(void);
|
|
#define __preempt_schedule() preempt_schedule()
|
|
|
|
#ifdef CONFIG_CONTEXT_TRACKING
|
|
extern asmlinkage void preempt_schedule_context(void);
|
|
#define __preempt_schedule_context() preempt_schedule_context()
|
|
#endif
|
|
#endif /* CONFIG_PREEMPT */
|
|
|
|
#endif /* __ASM_PREEMPT_H */
|