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DateTue, 21 Dec 2010 20:17:33 +0200
FromAvi Kivity <>
SubjectRe: [RFC PATCH 15/15] nohz_task: Procfs interface
On 12/21/2010 07:05 PM, Frederic Weisbecker wrote:
> >
> > For an example of a per-cpu flag that is checked on every exit with
> > zero additional overhead on the flag clear case, look at
> > TIF_USER_RETURN_NOTIFY.
>
> Right, but the problem is actually that if we want to automate the nohz
> attribute on every tasks, then you need you have this flag set for
> all of these threads.
>
> No problem with that, but if nobody wants the nohz attribute, we don't
> need to force that slow path.

When the scheduler detects the task is all alone, it sets the flag; when
it blocks, or if another task joins, it drops the flag (at most one task
per cpu has the flag set).

Does that work?

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.



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