lkml.org 
[lkml]   [2015]   [Mar]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v10 04/11] sched: Make sched entity usage tracking scale-invariant
On Tue, Mar 24, 2015 at 11:00:57AM +0100, Vincent Guittot wrote:
> On 23 March 2015 at 14:19, Peter Zijlstra <peterz@infradead.org> wrote:
> > On Fri, Feb 27, 2015 at 04:54:07PM +0100, Vincent Guittot wrote:
> >
> >> + unsigned long scale_freq = arch_scale_freq_capacity(NULL, cpu);
> >
> >> + sa->running_avg_sum += delta_w * scale_freq
> >> + >> SCHED_CAPACITY_SHIFT;
> >
> > so the only thing that could be improved is somehow making this
> > multiplication go away when the arch doesn't implement the function.
> >
> > But I'm not sure how to do that without #ifdef.
> >
> > Maybe a little something like so then... that should make the compiler
> > get rid of those multiplications unless the arch needs them.
>
> yes, it removes useless multiplication when not used by an arch.
> It also adds a constraint on the arch side which have to define
> arch_scale_freq_capacity like below:
>
> #define arch_scale_freq_capacity xxx_arch_scale_freq_capacity
> with xxx_arch_scale_freq_capacity an architecture specific function

Yeah, but it not being weak should make that a compile time warn/fail,
which should be pretty easy to deal with.

> If it sounds acceptable i can update the patch with your proposal ?

I'll stick it to the end, I just wanted to float to patch to see if
people had better solutions.


\
 
 \ /
  Last update: 2015-03-25 18:41    [W:0.255 / U:0.028 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site