Re: [PATCH 1/2] x86/dumpstack: Optimize save_stack_trace
From: Byungchul Park
Date: Sun Jul 17 2016 - 22:39:42 EST
On Fri, Jul 08, 2016 at 12:08:19PM +0200, Ingo Molnar wrote:
> * Byungchul Park <byungchul.park@xxxxxxx> wrote:
> > On Mon, Jul 04, 2016 at 07:27:54PM +0900, Byungchul Park wrote:
> > > I suggested this patch on https://lkml.org/lkml/2016/6/20/22. However,
> > > I want to proceed saperately since it's somewhat independent from each
> > > other. Frankly speaking, I want this patchset to be accepted at first so
> > > that the crossfeature can use this optimized save_stack_trace_norm()
> > > which makes crossrelease work smoothly.
> > What do you think about this way to improve it?
> I like both of your improvements, the speed up is impressive:
> [ 2.327597] save_stack_trace() takes 87114 ns
> [ 2.781694] save_stack_trace() takes 20044 ns
> [ 3.103264] save_stack_trace takes 3821 (sched_lock)
> Could you please also measure call graph recording (perf record -g), how much
> faster does it get with your patches and what are our remaining performance hot
Of course, I will.
> Could you please merge your patches to the latest -tip tree, because this commit I
> merged earlier today:
> 81c2949f7fdc x86/dumpstack: Add show_stack_regs() and use it
> conflicts with your patches. (I'll push this commit out later today.)
> Also, could you please rename the _norm names to _fast or so, to signal that this
> is a faster but less reliable method to get a stack dump? Nobody knows what
> '_norm' means, but '_fast' is pretty self-explanatory.
It would be better.