Re: [PATCH v4 10/11] perf/x86/intel: Perform rotation on Intel CQM RMIDs

From: Matt Fleming
Date: Fri Jan 09 2015 - 07:14:16 EST


On Tue, 06 Jan, at 06:17:12PM, Peter Zijlstra wrote:
>
> afaict the again label will try and steal yet another rmid, if rmids
> don't decay fast enough, we could end up with all rmids on the limbo
> list and none active. Or am I missing something here?

You're not missing anything, that's true, we will try and steal more
RMIDs. We could perhaps put a limit on how many RMIDs we're willing to
steal, but I think it should definitely be > 1 because RMIDs can
stabilize out of order.

It's worth pointing out that we only steal more RMIDs if the ones on the
limbo list have been queued for the "minimum queue time" - it really is
a last resort.

--
Matt Fleming, Intel Open Source Technology Center
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