Re: linux hrtimer affinity

[Peter Teoh <htmldeveloper@xxxxxxxxx>]

On Wed, Feb 15, 2012 at 12:06 AM, Vimal <j.vimal@xxxxxxxxx> wrote:

Hi all,

Is there a way to set the affinity of hrtimer callback, so that it
executes on a particular logical CPU?

The reason is that I have a hrtimer callback that executes a tasklet.

 If the timer callback executes on a different CPU than the one it was
enqueued in, then the tasklet is scheduled on the same CPU, which
makes it difficult to reason serialising locks to per-CPU data

How about this:

http://www.makelinux.net/ldd3/chp-7-sect-5

Tasklet is executed and scheduled on a particular known cpu,  so unless u spawn another tasklet that execute on the other CPU, u don't need per-CPU data structure - simply because there is no another CPU to contend with the data structure.   Not sure if I got the point?

I am not sure why u need to synchronize stuff "between CPU", as a particular tasklet is only executed on only one CPU at a time:

I suspect what u wanted is a "task".   A tasklet is effectively a "bottom half" and u are holding a spinlock while executing it, and thus it really has to be very fast.   Read this paper:

http://www.wil.cx/matthew/lca2003/paper.pdf

structures.

Any ideas?

Thanks,
--
Vimal

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-- 
Regards,
Peter Teoh
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