linux-kernel - Re: [PATCH] perf/core: introduce context per CPU event list

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Date:   Thu, 10 Nov 2016 17:26:32 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     kan.liang@...el.com, mingo@...hat.com,
        linux-kernel@...r.kernel.org, acme@...nel.org, tglx@...utronix.de,
        alexander.shishkin@...ux.intel.com, vince@...ter.net,
        eranian@...gle.com, andi@...stfloor.org
Subject: Re: [PATCH] perf/core: introduce context per CPU event list

On Thu, Nov 10, 2016 at 02:10:37PM +0000, Mark Rutland wrote:

> Sure, that sounds fine for scheduling (including big.LITTLE).
> 
> I might still be misunderstanding something, but I don't think that
> helps Kan's case: since INACTIVE events which will fail their filters
> (including the CPU check) will still be in the tree, they will still
> have to be iterated over.
> 
> That is, unless we also sort the tree by event->cpu, or if in those
> cases we only care about ACTIVE events and can use an active list.

A few emails back up I wrote:

>> If we stick all events in an RB-tree sorted on: {pmu,cpu,runtime} we

Looking at the code there's also cgroup muck, not entirely sure where in
the sort order that should go if at all.

But having pmu and cpu in there would cure the big-little and
per-task-per-cpu event issues.