linux-kernel - Re: [PATCH v4 05/12] arm-cci: PMU: Add support for transactions

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Message-ID: <5673DFC7.6060406@arm.com>
Date:	Fri, 18 Dec 2015 10:28:23 +0000
From:	"Suzuki K. Poulose" <Suzuki.Poulose@....com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	mark.rutland@....com, punit.agrawal@....com, arm@...nel.org
Subject: Re: [PATCH v4 05/12] arm-cci: PMU: Add support for transactions

On 17/12/15 18:42, Peter Zijlstra wrote:
> On Thu, Dec 17, 2015 at 05:49:12PM +0000, Suzuki K. Poulose wrote:
>> We keep track of only the 'ADD' transactions. While we are in a
>> transaction, we keep track of the indices allocated for the events
>> and delay the following operations until the transaction is committed.
>>   1) Programming the event on the counter
>>   2) Enabling the counter
>>   3) Setting the period for the event.
>
> So that's not really what the txn interface is for, its meant to
> amortize event scheduling.

OK

>
> The above doesn't look like it has a failure case, in which case you can
> achieve the same simpler, using pmu::pmu_{dis,en}able().
>

I thought about that, but was not sure if pmu->stop() is guaranteed to be
called on all the events scheduled on the PMU when we pmu::pmu_disable().
Is it ?

Thanks for the quick response.

Suzuki
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