linux-kernel - Re: [PATCH 1/3] arm/pmu: Reject groups spanning multiple hardware PMUs

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Date:	Tue, 10 Mar 2015 12:00:49 +0000
From:	"Suzuki K. Poulose" <Suzuki.Poulose@....com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Will Deacon <Will.Deacon@....com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"acme@...nel.org" <acme@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Punit Agrawal <Punit.Agrawal@....com>,
	Pawel Moll <Pawel.Moll@....com>,
	Mark Rutland <Mark.Rutland@....com>
Subject: Re: [PATCH 1/3] arm/pmu: Reject groups spanning multiple hardware
 PMUs

On 10/03/15 11:27, Peter Zijlstra wrote:
> On Mon, Mar 09, 2015 at 12:46:30PM +0000, Suzuki K. Poulose wrote:
>> From: "Suzuki K. Poulose" <suzuki.poulose@....com>
>>
>> Don't allow grouping hardware events from different PMUs
>>   (eg. CCI + CPU).
>
> Uhm, how does this work? If we have multiple hardware PMUs we'll stop
> scheduling events after the first failed event schedule. This can leave
> one of the PMUs severely under utilized.
This is done from pmu->event_init(), where we haven't scheduled an
event yet. Do you think we need to solve it using a different approach
? What is the best way to handle this situation ? Is it OK
to allow different PMUs in the group ?

Suzuki
>


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