lkml.org 
[lkml]   [2016]   [Oct]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 1/7] sched/fair: Update the rq clock before detaching tasks
On Mon, 03 Oct, at 02:49:07PM, Peter Zijlstra wrote:
> On Wed, Sep 21, 2016 at 02:38:07PM +0100, Matt Fleming wrote:
> > detach_task_cfs_rq() may indirectly call rq_clock() to inform the
> > cpufreq code that the rq utilisation has changed. In which case, we
> > need to update the rq clock.
>
> Hurm,. so it would've been good to know the callchain that got you
> there.
>
> There's two functions that use detach_task_cfs_rq(), one is through
> sched_change_group() and that does indeed lack a rq_clock update.
>
> The other is through switched_from() where its far harder (but still
> possible afaict) to miss the update.

It was the former callchain.

> Now, neither cases are really fast paths, but it would be good to try
> and avoid too many update_rq_clock() calls in the same rq-lock section.
> So I'm not entirely sure about the placement here.
>
> But let me go stare at the actual debug framework thing first.. I think
> this patch is fallout/fixups from that.

\
 
 \ /
  Last update: 2016-10-03 16:38    [W:0.274 / U:1.692 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site