From: Peter Zijlstra <peterz@infradead.org>
To: mark.barnett@arm.com
Cc: 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 v3 3/5] perf: Allow adding fixed random jitter to the alternate sampling period
Date: Tue, 11 Mar 2025 12:37:27 +0100 [thread overview]
Message-ID: <20250311113727.GB9968@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20250311113128.GD19424@noisy.programming.kicks-ass.net>
On Tue, Mar 11, 2025 at 12:31:29PM +0100, Peter Zijlstra wrote:
> + sample_period = hwc->sample_period_base;
> + if (hwc->state & PERF_HES_HF_RAND) {
> + u64 rand = 1 << event->attr.hf_sample_rand;
> + sample_period -= rand / 2;
> + sample_period += prandom_u32_state(&perf_rand) & (rand - 1);
> + }
> + if (hwc->state & PERF_HES_HF_ON) {
> + u64 hf_sample_period = event->attr.hf_sample_period;
> +
> + if (sample_period < hf_sample_period) {
> + hwc->state &= ~PERF_HES_HF_ON;
> + goto set_period;
> + }
> +
> + if (!(hwc->state & PERF_HES_HF_SAMPLE)) {
> + hwc->sample_period -= hf_sample_period;
> + hwc->state |= PERF_HES_HF_SAMPLE;
> + } else {
> + hwc->sample_period = hf_sample_period;
> + hwc->state &= ~PERF_HES_HF_SAMPLE;
and obviously this should be the local sample_period modified above, not
the hwc one.
> + }
> + }
> +set_period:
> + hwc->sample_period = sample_period;
next prev parent reply other threads:[~2025-03-11 11:37 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-07 20:22 [PATCH v3 0/5] A mechanism for efficient support for per-function metrics mark.barnett
2025-03-07 20:22 ` [PATCH v3 1/5] perf: Record sample last_period before updating mark.barnett
2025-03-07 20:22 ` [PATCH v3 2/5] perf: Allow periodic events to alternate between two sample periods mark.barnett
2025-03-10 12:44 ` Peter Zijlstra
2025-03-07 20:22 ` [PATCH v3 3/5] perf: Allow adding fixed random jitter to the alternate sampling period mark.barnett
2025-03-10 12:47 ` Peter Zijlstra
2025-03-10 16:27 ` Mark Barnett
2025-03-11 11:31 ` Peter Zijlstra
2025-03-11 11:35 ` Peter Zijlstra
2025-03-12 10:44 ` Peter Zijlstra
2025-03-11 11:37 ` Peter Zijlstra [this message]
2025-03-11 17:22 ` Mark Barnett
2025-03-12 9:39 ` Peter Zijlstra
2025-03-07 20:22 ` [PATCH v3 4/5] tools/perf: Modify event parser to support alt-period term mark.barnett
2025-03-07 20:22 ` [PATCH v3 5/5] tools/perf: Modify event parser to support alt-period-jitter term mark.barnett
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