linux-kernel - Re: [[PATCH v6 09/10] powerpc/perf/hv-24x7: Use PMU_TXN

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Message-ID: <20150908112900.GF3644@twins.programming.kicks-ass.net>
Date:	Tue, 8 Sep 2015 13:29:00 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Michael Ellerman <mpe@...erman.id.au>
Cc:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-s390@...r.kernel.org, sparclinux@...r.kernel.org
Subject: Re: [[PATCH v6 09/10] powerpc/perf/hv-24x7: Use PMU_TXN_READ
 interface

On Tue, Sep 08, 2015 at 07:07:55PM +1000, Michael Ellerman wrote:
> On Thu, 2015-09-03 at 20:07 -0700, Sukadev Bhattiprolu wrote:
> > The 24x7 counters in Powerpc allow monitoring a large number of counters
> > simultaneously. They also allow reading several counters in a single
> > HCALL so we can get a more consistent snapshot of the system.
> > 
> > Use the PMU's transaction interface to monitor and read several event
> > counters at once. The idea is that users can group several 24x7 events
> > into a single group of events. We use the following logic to submit
> > the group of events to the PMU and read the values:
> > 
> > 	pmu->start_txn()		// Initialize before first event
> > 
> > 	for each event in group
> > 		pmu->read(event);	// Queue each event to be read
> > 
> > 	pmu->commit_txn()		// Read/update all queuedcounters
> > 
> > The ->commit_txn() also updates the event counts in the respective
> > perf_event objects.  The perf subsystem can then directly get the
> > event counts from the perf_event and can avoid submitting a new
> > ->read() request to the PMU.
> > 
> > Thanks to input from Peter Zijlstra.
> > 
> > Signed-off-by: Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
> > ---
> >  arch/powerpc/perf/hv-24x7.c |  166 ++++++++++++++++++++++++++++++++++++++++++-
> 
> This looks fine to me from an arch perspective. I assume the whole series can
> go via tip-something?

Yeah, I've had it queued for a few days, there was one s390 compile
fail reported by the build-bot, which I've just fixed. So if nothing
weird happens, it should hit tip somewhere this week.

> Acked-by: Michael Ellerman <mpe@...erman.id.au>

Thanks!
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