Re: [tip:x86/asm] x86: Speed up ___preempt_schedule*() by using THUNK helpers

[Oleg Nesterov]

On 10/03, Chuck Ebbert wrote:
>
> > [  921.917752] ? ___preempt_schedule_context (arch/x86/lib/thunk_64.S:44)
> > [  921.917752] ? preempt_schedule_context (kernel/context_tracking.c:145)
> > [  921.917752] ? ___preempt_schedule_context (arch/x86/lib/thunk_64.S:44)
> > [  921.917752] ? preempt_schedule_context (kernel/context_tracking.c:145)
> > [  921.917752] ? ___preempt_schedule_context (arch/x86/lib/thunk_64.S:44)
> > [  921.917752] ? preempt_schedule_context (kernel/context_tracking.c:145)
> > [  921.917752] ? ___preempt_schedule_context (arch/x86/lib/thunk_64.S:44)
> > [  921.917752] ? preempt_schedule_context (kernel/context_tracking.c:145)
> > [  921.917752] ? ___preempt_schedule_context (arch/x86/lib/thunk_64.S:44)
> > [  921.917752] ? preempt_schedule_context (kernel/context_tracking.c:145)
>
> <snip lots of repeats of this>
>
> I *think* this is because RBP isn't being saved across task switch
> anymore?
>
> Without CONFIG_FRAME_POINTERS that night not be a problem...

Could you please spell?

I don't even understand "RBP isn't being saved", SAVE_CONTEXT/RESTORE_CONTEXT
do push/pop %rbp?

Thanks,

Oleg.

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