From: Leo Yan <leo.yan@arm.com>
To: Mark Barnett <mark.barnett@arm.com>
Cc: peterz@infradead.org, mingo@redhat.com, acme@kernel.org,
namhyung@kernel.org, irogers@google.com, ben.gainey@arm.com,
deepak.surti@arm.com, ak@linux.intel.com, will@kernel.org,
james.clark@arm.com, mark.rutland@arm.com,
alexander.shishkin@linux.intel.com, jolsa@kernel.org,
adrian.hunter@intel.com, linux-perf-users@vger.kernel.org,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 1/5] perf: Allow periodic events to alternate between two sample periods
Date: Mon, 10 Mar 2025 10:55:51 +0000 [thread overview]
Message-ID: <20250310105551.GB9682@e132581.arm.com> (raw)
In-Reply-To: <c62a9f8a-312d-4f9e-9022-265e53564101@arm.com>
On Fri, Mar 07, 2025 at 08:28:13PM +0000, Mark Barnett wrote:
> On 1/21/25 13:01, Leo Yan wrote:
> > > local64_set(&hwc->period_left, hwc->sample_period);
> > > + if (attr->alt_sample_period) {
> > > + hwc->sample_period = attr->alt_sample_period;
> > > + hwc->using_alt_sample_period = true;
> > > + }
> >
> > My understanding it sets a short sample window for the first period.
> > Would it initialize the `hwc->period_left` with the updated sample
> > period?
> >
>
> It sets the long period first: hwc->period_left is used to program the PMU
> when setting up the event, and hwc->sample_period is queued up as the next
> period to switch to.
Makes sense to me. Thanks for explanation.
Leo
next prev parent reply other threads:[~2025-03-10 11:32 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-01-06 12:01 [PATCH v2 0/5] A mechanism for efficient support for per-function metrics mark.barnett
2025-01-06 12:01 ` [PATCH v2 1/5] perf: Allow periodic events to alternate between two sample periods mark.barnett
2025-01-21 13:01 ` Leo Yan
2025-03-07 20:28 ` Mark Barnett
2025-03-10 10:55 ` Leo Yan [this message]
2025-01-31 18:44 ` Rob Herring
2025-02-07 19:18 ` Mark Barnett
2025-01-06 12:01 ` [PATCH v2 2/5] perf: Allow adding fixed random jitter to the alternate sampling period mark.barnett
2025-01-06 12:01 ` [PATCH v2 3/5] tools/perf: Modify event parser to support alt-period term mark.barnett
2025-01-06 12:01 ` [PATCH v2 4/5] tools/perf: Modify event parser to support alt-period-jitter term mark.barnett
2025-01-06 12:01 ` [PATCH v2 5/5] perf: Record sample last_period before updating mark.barnett
2025-01-21 17:22 ` Leo Yan
2025-01-22 5:03 ` kernel test robot
2025-01-22 16:47 ` [PATCH v2 0/5] A mechanism for efficient support for per-function metrics James Clark
2025-02-07 19:23 ` Mark Barnett
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