linux-kernel - Re: [PATCH 2/4] perf: Add filter_match() as a parameter for pinned/flexible_sched

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Message-ID: <20190429165634.GD2182@lakrids.cambridge.arm.com>
Date:   Mon, 29 Apr 2019 17:56:34 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     "Liang, Kan" <kan.liang@...ux.intel.com>
Cc:     peterz@...radead.org, tglx@...utronix.de, mingo@...hat.com,
        linux-kernel@...r.kernel.org, eranian@...gle.com, tj@...nel.org,
        ak@...ux.intel.com
Subject: Re: [PATCH 2/4] perf: Add filter_match() as a parameter for
 pinned/flexible_sched_in()

On Mon, Apr 29, 2019 at 11:31:26AM -0400, Liang, Kan wrote:
> 
> 
> On 4/29/2019 11:12 AM, Mark Rutland wrote:
> > On Mon, Apr 29, 2019 at 07:44:03AM -0700, kan.liang@...ux.intel.com wrote:
> > > From: Kan Liang <kan.liang@...ux.intel.com>
> > > 
> > > A fast path will be introduced in the following patches to speed up the
> > > cgroup events sched in, which only needs a simpler filter_match().
> > > 
> > > Add filter_match() as a parameter for pinned/flexible_sched_in().
> > > 
> > > No functional change.
> > 
> > I suspect that the cost you're trying to avoid is pmu_filter_match()
> > iterating over the entire group, which arm systems rely upon for correct
> > behaviour on big.LITTLE systems.
> > 
> > Is that the case?
> 
> No. In X86, we don't use pmu_filter_match(). The fast path still keeps this
> filter.
> perf_cgroup_match() is the one I want to avoid.

Understood; sorry for the silly question, and thanks for confirming! :)

Thanks,
Mark.