Messages in this thread | | | Subject | Re: [PATCH v1] sched: there is no need to call switch_mm_irqs_off when sched between two user thread. | From | Ming Wang <> | Date | Wed, 1 Jun 2022 14:45:06 +0800 |
| |
On 2022/5/31 下午10:46, Peter Zijlstra wrote: > On Tue, May 31, 2022 at 07:56:41PM +0800, Ming Wang wrote: >> When condition (prev->active_mm == next->mm && !prev->mm) is met, >> the situation is as follows: >> >> user thread -> user thread >> >> There is not need switch_mm when sched between two user thread. >> Because they share the mm_struct. This can provide better >> performance when testing UnixBench. >> >> Signed-off-by: Ming Wang <wangming01@loongson.cn> >> --- >> kernel/sched/core.c | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/kernel/sched/core.c b/kernel/sched/core.c >> index 696c649..9d7f6fb 100644 >> --- a/kernel/sched/core.c >> +++ b/kernel/sched/core.c >> @@ -5099,7 +5099,8 @@ asmlinkage __visible void schedule_tail(struct task_struct *prev) >> * case 'prev->active_mm == next->mm' through >> * finish_task_switch()'s mmdrop(). >> */ >> - switch_mm_irqs_off(prev->active_mm, next->mm, next); >> + if ((prev->active_mm != next->mm) || (!prev->mm)) >> + switch_mm_irqs_off(prev->active_mm, next->mm, next); > I think this needs to be inside switch_mm(). Architectures are free to > play silly games with what the current active mm is (and iirc x86 > actually does this). ok, thanks! And I will do it in architecture code.
| |