From: Charlie Jenkins <charlie@rivosinc.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@kernel.org>, Ian Rogers <irogers@google.com>,
Adrian Hunter <adrian.hunter@intel.com>,
Atish Patra <atishp@rivosinc.com>,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 1/3] perf: Add PERF_EVENT_IOC_INC_EVENT_LIMIT
Date: Mon, 13 Jan 2025 10:59:29 -0800 [thread overview]
Message-ID: <Z4VikUrFuHocTXAl@ghost> (raw)
In-Reply-To: <20250113131812.GB8362@noisy.programming.kicks-ass.net>
On Mon, Jan 13, 2025 at 02:18:12PM +0100, Peter Zijlstra wrote:
> On Mon, Jan 06, 2025 at 08:07:32PM -0800, Charlie Jenkins wrote:
> > PERF_EVENT_IOC_REFRESH immediately enables after incrementing
> > event_limit. Provide a new ioctl flag that allows programs to increment
> > event_limit without enabling the event. A usecase for this is to set an
> > event_limit in combination with enable_on_exec.
>
>
> Utter lack of WHY.
My usecase is being able to use libperf to calculate performance metrics
from running a program for X number of instructions.
PERF_EVENT_IOC_REFRESH can be used to stop the counters after the
instruction sampling threshold has been hit. This requires being able to
start PERF_EVENT_IOC_REFRESH as soon as the program starts executing,
which is a perfect application for enable_on_exec.
- Charlie
next prev parent reply other threads:[~2025-01-13 18:59 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-01-07 4:07 [PATCH v3 0/3] perf: Add PERF_EVENT_IOC_INC_EVENT_LIMIT Charlie Jenkins
2025-01-07 4:07 ` [PATCH v3 1/3] " Charlie Jenkins
2025-01-13 13:18 ` Peter Zijlstra
2025-01-13 18:59 ` Charlie Jenkins [this message]
2025-01-07 4:07 ` [PATCH v3 2/3] perf: Document PERF_EVENT_IOC_INC_EVENT_LIMIT Charlie Jenkins
2025-01-07 4:07 ` [PATCH v3 3/3] libperf: Add perf_evsel__refresh() function Charlie Jenkins
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