From: Peter Zijlstra <peterz@infradead.org>
To: Andi Kleen <ak@linux.intel.com>
Cc: "Liang, Kan" <kan.liang@linux.intel.com>,
mingo@redhat.com, acme@kernel.org, linux-kernel@vger.kernel.org,
mark.rutland@arm.com, alexander.shishkin@linux.intel.com,
jolsa@kernel.org, namhyung@kernel.org, irogers@google.com,
adrian.hunter@intel.com, eranian@google.com,
alexey.v.bayduraev@linux.intel.com, tinghao.zhang@intel.com,
Sandipan Das <sandipan.das@amd.com>,
Ravi Bangoria <ravi.bangoria@amd.com>,
Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Subject: Re: [RESEND PATCH V3 1/6] perf: Add branch stack extra
Date: Tue, 3 Oct 2023 18:33:00 +0200 [thread overview]
Message-ID: <20231003163300.GF1539@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <ZRwuE8LPkwtkjX5C@tassilo>
On Tue, Oct 03, 2023 at 08:06:59AM -0700, Andi Kleen wrote:
> > I'm thinking we should do something like expose branch_counter_nr and
> > branch_counter_width in the sysfs node, and then rename this extra field
> > to counters.
> >
> > Then userspace can do something like:
> >
> > for (i = 0; i < branch_counter_nr; i++) {
> > counter[i] = counters & ((1 << branch_counter_width) - 1);
> > counters >>= branch_counter_width;
> > }
> >
> > to extract the actual counter values.
>
> perf script/report won't necessarily have access to the sysfs
> values if they run on a different system
>
> It would need extra PT style metadata written by perf record to
> perf.data and read by the user tools.
>
> Seems complicated. It would be better if it just parsed on its own.
Well, you really don't want to repeat the 4,2 thing in every event, that
seems daft (and a waste of space, because how large do we want those
fields to be etc..).
We don't really have a better place for these sorts of things. And yeah,
the PT thing sets precedent here.
next prev parent reply other threads:[~2023-10-03 16:33 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-11 15:48 [RESEND PATCH V3 1/6] perf: Add branch stack extra kan.liang
2023-09-11 15:48 ` [RESEND PATCH V3 2/6] perf/x86: Add PERF_X86_EVENT_NEEDS_BRANCH_STACK flag kan.liang
2023-09-11 15:48 ` [RESEND PATCH V3 3/6] perf: Add branch_sample_call_stack kan.liang
2023-09-11 15:48 ` [RESEND PATCH V3 4/6] perf/x86/intel: Support LBR event logging kan.liang
2023-09-11 15:48 ` [RESEND PATCH V3 5/6] tools headers UAPI: Sync include/uapi/linux/perf_event.h header with the kernel kan.liang
2023-09-11 15:48 ` [RESEND PATCH V3 6/6] perf tools: Add branch event knob kan.liang
2023-10-02 13:49 ` [RESEND PATCH V3 1/6] perf: Add branch stack extra Liang, Kan
2023-10-02 15:45 ` Peter Zijlstra
2023-10-02 19:19 ` Liang, Kan
2023-10-02 21:37 ` Peter Zijlstra
2023-10-03 0:57 ` Liang, Kan
2023-10-03 10:27 ` Peter Zijlstra
2023-10-03 12:57 ` Liang, Kan
2023-10-03 15:06 ` Andi Kleen
2023-10-03 15:58 ` Liang, Kan
2023-10-03 16:33 ` Peter Zijlstra [this message]
2023-10-03 16:55 ` Andi Kleen
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