From: David Carrillo-Cisneros <davidcc@google.com>
To: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Mark Rutland <mark.rutland@arm.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
vince@deater.net, Stephane Eranian <eranian@google.com>,
Andi Kleen <andi@firstfloor.org>, Kan Liang <kan.liang@intel.com>,
Vikas Shivappa <vikas.shivappa@linux.intel.com>
Subject: Re: [PATCH] perf/core: introduce context per CPU event list
Date: Sun, 1 Jan 2017 13:18:27 -0800 [thread overview]
Message-ID: <CALcN6miCejPbqGnSj5wNY18BGeS-pQmeV07RM4FN3+fL1hnwxw@mail.gmail.com> (raw)
In-Reply-To: <1483302059-4334-1-git-send-email-davidcc@google.com>
On Sun, Jan 1, 2017 at 12:20 PM, David Carrillo-Cisneros
<davidcc@google.com> wrote:
> From: Mark Rutland <mark.rutland@arm.com>
>
> On Thu, Nov 10, 2016 at 05:26:32PM +0100, Peter Zijlstra wrote:
>> 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
>
> Ah, sorry. Clearly I wouldn't pass a reading comprehension test today.
>
>> 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.
>
> Yup, that all makes sense to me now (modulo the cgroup stuff I also
> haven't considered yet).
cgroup events are stored in each pmu's cpuctx, so they wouldn't benefit
from a pmu,cpu sort order. Yet the RB-tree would help if it could use cgroup
as key for cpu contexts.
Is there a reason to have runtime as part of the RB-tree?
Couldn't a FIFO list work just fine? A node could have an ACTIVE and
an INACTIVE FIFO list and just move the events in out the tree in ioctl and
to/from ACTIVE from/to INACTIVE on sched in/out.
This would speed up both sched in and sched out.
The node would be something like this:
struct ctx_rbnode {
struct rb_node node;
struct list_head active_events;
struct list_head inactive_events;
};
And the insertion order would be {pmu, cpu} for task contexts (cpu == -1
for events without fixed cpu) and {cgroup} for cpuctxs (CPU events would
have NULL cgrp).
Am I interested on getting this to work as part of the cgroup context switch
optimization that CQM/CMT needs. See discussion in:
https://patchwork.kernel.org/patch/9478617/
Is anyone actively working on it?
Thanks,
David
next prev parent reply other threads:[~2017-01-01 21:18 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-09 19:04 [PATCH] perf/core: introduce context per CPU event list kan.liang
2016-11-10 8:33 ` Peter Zijlstra
2016-11-10 11:05 ` Mark Rutland
2016-11-10 11:37 ` Peter Zijlstra
2016-11-10 12:04 ` Mark Rutland
2016-11-10 12:12 ` Peter Zijlstra
2016-11-10 12:26 ` Mark Rutland
2016-11-10 12:58 ` Peter Zijlstra
2016-11-10 14:10 ` Mark Rutland
2016-11-10 14:31 ` Liang, Kan
2016-11-10 16:26 ` Peter Zijlstra
2016-11-10 17:01 ` Mark Rutland
[not found] ` <1483302059-4334-1-git-send-email-davidcc@google.com>
2017-01-01 21:18 ` David Carrillo-Cisneros [this message]
2017-01-03 12:00 ` Mark Rutland
2017-01-04 0:39 ` David Carrillo-Cisneros
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