Re: [[PATCH v6 09/10] powerpc/perf/hv-24x7: Use PMU_TXN_READ interface

On Tue, 2015-09-08 at 13:29 +0200, Peter Zijlstra wrote:

On Tue, Sep 08, 2015 at 07:07:55PM +1000, Michael Ellerman wrote:

quoted

On Thu, 2015-09-03 at 20:07 -0700, Sukadev Bhattiprolu wrote:

quoted

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 <redacted>
---
 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.

Great, thanks.

Now Sukadev can focus on getting the JSON events support merged, hopefully it
won't require another 16 versions.

cheers