lkml.org 
[lkml]   [2014]   [Apr]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [Query]: tick-sched: why don't we stop tick when we are running idle task?
On Mon, Apr 14, 2014 at 02:06:00PM +0200, Peter Zijlstra wrote:
> On Mon, Apr 14, 2014 at 05:22:30PM +0530, Viresh Kumar wrote:
> > On 14 April 2014 17:17, Peter Zijlstra <peterz@infradead.org> wrote:
> > > What causes this tick? I was under the impression that once there's a
> > > single task (not doing any syscalls) and the above issues are sorted, no
> > > more tick would happen.
> >
> > This is what Frederic told me earlier:
> >
> > https://lkml.org/lkml/2014/2/13/238
>
> That's a bit of a non-answer. I'm fairly sure its not a gazillion
> issues, since the actual scheduler tick doesn't actually do that much.
>
> So start by enumerating what is actually required.

Ok, I'm a bit buzy with a conference right now but I'm going to summarize that
soonish.

>
> The 2), which I suppose you're now trying to implement is I think
> entirely the wrong way. The tick really assumes it runs local, moving it
> to another CPU is insane.

There is probably a few things that assume local calls but last time
I checked I had the impression that it was fairly possible to call sched_class::task_tick()
remotely. rq is locked, no reference to "current", use rq accessors...

OTOH scheduler_tick() itself definetly requires local calls.


\
 
 \ /
  Last update: 2014-04-15 11:41    [W:0.079 / U:38.924 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site