Re: [v4 RFC PATCH 1/4] timers: Framework for identifying pinnedtimers

From: Arun R Bharadwaj
Date: Thu Apr 02 2009 - 01:09:37 EST


* Andi Kleen <andi@xxxxxxxxxxxxxx> [2009-04-01 13:41:46]:

> On Wed, Apr 01, 2009 at 05:02:58PM +0530, Arun R Bharadwaj wrote:
> > * Arun R Bharadwaj <arun@xxxxxxxxxxxxxxxxxx> [2009-04-01 17:01:28]:
> >
> > This patch creates a new framework for identifying cpu-pinned timers
> > and hrtimers.
> >
> >
> > This framework is needed because pinned timers are expected to fire on
> > the same CPU on which they are queued. So it is essential to identify
> > these and not migrate them, in case there are any.
>
> How would that interact with add_timer_on()? You currently only
> support the current CPU, don't you?
>
> e.g. the new tip x86 machine check polling code relies on add_timer_on
> staying on that CPU.
>

Pinned timers are directly related to add_timer_on().
So I assume that whatever timer is queued using add_timer_on() is
supposed to be a pinned timer.
Currently, we can stay on one CPU and still queue a pinned timer on
some other CPU. We can mark those timers as 'pinned' to that
particular CPU.

--arun

> -Andi
>
> --
> ak@xxxxxxxxxxxxxxx -- Speaking for myself only.
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