linux-kernel - Re: [tip:perf/core] perf: Add group scheduling transactional APIs

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Date:	Fri, 07 May 2010 23:55:55 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	mingo@...hat.com, hpa@...or.com, eranian@...gle.com,
	paulus@...ba.org, linux-kernel@...r.kernel.org,
	davem@...emloft.net, fweisbec@...il.com, ming.m.lin@...el.com,
	tglx@...utronix.de, mingo@...e.hu
Cc:	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:perf/core] perf: Add group scheduling transactional APIs

On Fri, 2010-05-07 at 18:44 +0000, tip-bot for Lin Ming wrote:
> Commit-ID:  6bde9b6ce0127e2a56228a2071536d422be31336
> Gitweb:     http://git.kernel.org/tip/6bde9b6ce0127e2a56228a2071536d422be31336
> Author:     Lin Ming <ming.m.lin@...el.com>
> AuthorDate: Fri, 23 Apr 2010 13:56:00 +0800
> Committer:  Ingo Molnar <mingo@...e.hu>
> CommitDate: Fri, 7 May 2010 11:31:02 +0200
> 
> perf: Add group scheduling transactional APIs
> 
> Add group scheduling transactional APIs to struct pmu.
> These APIs will be implemented in arch code, based on Peter's idea as
> below.
> 
> > the idea behind hw_perf_group_sched_in() is to not perform
> > schedulability tests on each event in the group, but to add the group
> > as a whole and then perform one test.
> >
> > Of course, when that test fails, you'll have to roll-back the whole
> > group again.
> >
> > So start_txn (or a better name) would simply toggle a flag in the pmu
> > implementation that will make pmu::enable() not perform the
> > schedulablilty test.
> >
> > Then commit_txn() will perform the schedulability test (so note the
> > method has to have a !void return value.
> >
> > This will allow us to use the regular
> > kernel/perf_event.c::group_sched_in() and all the rollback code.
> > Currently each hw_perf_group_sched_in() implementation duplicates all
> > the rolllback code (with various bugs).
> 
> ->start_txn:
> Start group events scheduling transaction, set a flag to make
> pmu::enable() not perform the schedulability test, it will be performed
> at commit time.
> 
> ->commit_txn:
> Commit group events scheduling transaction, perform the group
> schedulability as a whole
> 
> ->cancel_txn:
> Stop group events scheduling transaction, clear the flag so
> pmu::enable() will perform the schedulability test.
> 
> Reviewed-by: Stephane Eranian <eranian@...gle.com>
> Reviewed-by: Frederic Weisbecker <fweisbec@...il.com>
> Signed-off-by: Lin Ming <ming.m.lin@...el.com>
> Cc: David Miller <davem@...emloft.net>
> Cc: Paul Mackerras <paulus@...ba.org>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> LKML-Reference: <1272002160.5707.60.camel@...ggr.sh.intel.com>
> Signed-off-by: Ingo Molnar <mingo@...e.hu> 


Paul, are you ok with the powerpc patch that goes with this:
  https://patchwork.kernel.org/patch/94620/

(I've got a slightly modified version because I did rename things back
to txn)

Dave already said he was OK with the sparc bits.

If you don't object, I'll push both patches to Ingo.

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