Messages in this thread | | | Date | Fri, 3 Oct 2014 17:48:14 -0500 | From | Chuck Ebbert <> | Subject | Re: [tip:x86/asm] x86: Speed up ___preempt_schedule*() by using THUNK helpers |
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On Fri, 3 Oct 2014 23:41:24 +0200 Oleg Nesterov <oleg@redhat.com> wrote:
> 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? >
SAVE_ARGS/RESTORE_ARGS, which is what THUNK uses, doesn't push/pop %rbp
Before, SAVE_ALL/RESTORE_ALL were being used around the call to preempt_schedule(). So from the symptoms I thought this was the problem.
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