Re: [RFC PATCH v16 8/8] perf test: Add test for Intel TPEBS counting mode

From: Namhyung Kim
Date: Thu Jul 11 2024 - 23:36:29 EST

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In reply to: Wang, Weilin: "RE: [RFC PATCH v16 8/8] perf test: Add test for Intel TPEBS counting mode"
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On Thu, Jul 11, 2024 at 3:05 PM Wang, Weilin <weilin.wang@xxxxxxxxx> wrote:
>
>
>
> > -----Original Message-----
> > From: Namhyung Kim <namhyung@xxxxxxxxxx>
> > Sent: Thursday, July 11, 2024 2:45 PM
> > To: Wang, Weilin <weilin.wang@xxxxxxxxx>
> > Cc: Ian Rogers <irogers@xxxxxxxxxx>; Arnaldo Carvalho de Melo
> > <acme@xxxxxxxxxx>; Peter Zijlstra <peterz@xxxxxxxxxxxxx>; Ingo Molnar
> > <mingo@xxxxxxxxxx>; Alexander Shishkin
> > <alexander.shishkin@xxxxxxxxxxxxxxx>; Jiri Olsa <jolsa@xxxxxxxxxx>; Hunter,
> > Adrian <adrian.hunter@xxxxxxxxx>; Kan Liang <kan.liang@xxxxxxxxxxxxxxx>;
> > linux-perf-users@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Taylor, Perry
> > <perry.taylor@xxxxxxxxx>; Alt, Samantha <samantha.alt@xxxxxxxxx>; Biggers,
> > Caleb <caleb.biggers@xxxxxxxxx>
> > Subject: Re: [RFC PATCH v16 8/8] perf test: Add test for Intel TPEBS counting
> > mode
> >
> > Hello,
> >
> > On Tue, Jul 09, 2024 at 06:23:51AM +0000, Wang, Weilin wrote:
> > > > On Mon, Jul 8, 2024 at 9:58 PM Wang, Weilin <weilin.wang@xxxxxxxxx>
> > > > wrote:
> > > > >
> > > > >
> > > > >
> > > > > > -----Original Message-----
> > > > > > From: Namhyung Kim <namhyung@xxxxxxxxxx>
> > > > > > Sent: Monday, July 8, 2024 9:44 PM
> > > > > > To: Wang, Weilin <weilin.wang@xxxxxxxxx>
> > > > > > Cc: Ian Rogers <irogers@xxxxxxxxxx>; Arnaldo Carvalho de Melo
> > > > > > <acme@xxxxxxxxxx>; Peter Zijlstra <peterz@xxxxxxxxxxxxx>; Ingo
> > Molnar
> > > > > > <mingo@xxxxxxxxxx>; Alexander Shishkin
> > > > > > <alexander.shishkin@xxxxxxxxxxxxxxx>; Jiri Olsa <jolsa@xxxxxxxxxx>;
> > Hunter,
> > > > > > Adrian <adrian.hunter@xxxxxxxxx>; Kan Liang
> > <kan.liang@xxxxxxxxxxxxxxx>;
> > > > > > linux-perf-users@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Taylor,
> > > > Perry
> > > > > > <perry.taylor@xxxxxxxxx>; Alt, Samantha <samantha.alt@xxxxxxxxx>;
> > > > Biggers,
> > > > > > Caleb <caleb.biggers@xxxxxxxxx>
> > > > > > Subject: Re: [RFC PATCH v16 8/8] perf test: Add test for Intel TPEBS
> > > > counting
> > > > > > mode
> > > > > >
> > > > > > Hello Weilin,
> > > > > >
> > > > > > On Sat, Jul 6, 2024 at 4:30 PM <weilin.wang@xxxxxxxxx> wrote:
> > > > > > >
> > > > > > > From: Weilin Wang <weilin.wang@xxxxxxxxx>
> > > > > > >
> > > > > > > Intel TPEBS sampling mode is supported through perf record. The
> > > > counting
> > > > > > mode
> > > > > > > code uses perf record to capture retire_latency value and use it in
> > metric
> > > > > > > calculation. This test checks the counting mode code.
> > > > > > >
> > > > > > > Signed-off-by: Weilin Wang <weilin.wang@xxxxxxxxx>
> > > > > > > ---
> > > > > > > .../perf/tests/shell/test_stat_intel_tpebs.sh | 18
> > > > ++++++++++++++++++
> > > > > > > 1 file changed, 18 insertions(+)
> > > > > > > create mode 100755 tools/perf/tests/shell/test_stat_intel_tpebs.sh
> > > > > > >
> > > > > > > diff --git a/tools/perf/tests/shell/test_stat_intel_tpebs.sh
> > > > > > b/tools/perf/tests/shell/test_stat_intel_tpebs.sh
> > > > > > > new file mode 100755
> > > > > > > index 000000000000..fea8cb1b8367
> > > > > > > --- /dev/null
> > > > > > > +++ b/tools/perf/tests/shell/test_stat_intel_tpebs.sh
> > > > > > > @@ -0,0 +1,18 @@
> > > > > > > +#!/bin/bash
> > > > > > > +# test Intel TPEBS counting mode
> > > > > > > +# SPDX-License-Identifier: GPL-2.0
> > > > > > > +
> > > > > > > +set -e
> > > > > > > +
> > > > > > > +# Use this event for testing because it should exist in all platforms
> > > > > > > +event=cache-misses:R
> > > > > > > +
> > > > > > > +# Without this cmd option, default value or zero is returned
> > > > > > > +echo "Testing without --record-tpebs"
> > > > > > > +result=$(perf stat -e "$event" true 2>&1)
> > > > > > > +[[ "$result" =~ $event ]] || exit 1
> > > > > > > +
> > > > > > > +# In platforms that do not support TPEBS, it should execute without
> > > > error.
> > > > > > > +echo "Testing with --record-tpebs"
> > > > > > > +result=$(perf stat -e "$event" --record-tpebs -a sleep 0.01 2>&1)
> > > > > >
> > > > > > It never finishes on my AMD machine.
> > > > > >
> > > > > Hi Namhyung,
> > > > >
> > > > > Do you see any message while it executes? Is the perf record forked
> > > > successfully
> > > > > but failed to return?
> > > >
> > > > I don't know.. all I can get is like below:
> > > >
> > > > $ sudo ./perf test tpebs -vv
> > > > 121: test Intel TPEBS counting mode:
> > > > --- start ---
> > > > test child forked, pid 583475
> > > > Testing without --record-tpebs
> > > > Testing with --record-tpebs
> > > > ^C
> > >
> > > I think the problem is that the forked "perf record" encountered error, which
> > > caused the control fifo failed to send a "ACK" back and the PIPE hanged.
> > >
> > > Could you please try out the diff below and see if the test would finish?
> > >
> > > As for the "perf record" error, I think it might because of the fake
> > > event(cache-misses:R) cannot be supported in AMD. Could you please test
> > run
> > > a "perf stat -e cache-misses:R --record-tpebs true" and see if it complains
> > about
> > > the event?
> >
> > So I tried the below patch and it worked.
> >
> > $ ./perf test -v tpebs
> > 121: test Intel TPEBS counting mode:
> > --- start ---
> > test child forked, pid 2190174
> > Testing without --record-tpebs
> > Testing with --record-tpebs
> > ---- end(-1) ----
> > 121: test Intel TPEBS counting mode : FAILED!
> >
> > It would be better if it can skip rather than fail on
> > non-supported machines.
> >
>
> Yes, I could add a check to only run the test on Intel platform.

Please do so.

>
> > Also I saw this message when I run the command manually.
> >
> > $ ./perf stat -e cache-misses:R --record-tpebs -v true
> > Control descriptor is not initialized
> > Retire_latency of event cache-misses:R is required
> > Prepare perf record for retire_latency
> > Error:
> > The cache-misses:pu event is not supported.
> > incompatible file format
> > incompatible file format (rerun with -v to learn more)
> > failed: did not received an ack
> > cache-misses:R: 0 1 1
> >
> > Performance counter stats for 'true':
> >
> > 0 cache-misses:R
> >
> > 0.000004939 seconds time elapsed
> >
> > 0.000000000 seconds user
> > 0.000000000 seconds sys
> >
> > I'm not sure why it showed the incompatible file format message.
> >
>
> The output matches with my expectation. I think the incompatible file format
> message is from the session open step of the sample reader thread.
>
> Because AMD CPU does not support cache-misses:p in "perf record", the control
> fifo does not receive a "ACK" message back from "perf record". Therefore, the
> ack_fd PIPE hanged and the test never ends.
>
> However, the sample reader thread opens the session in parallel. Because the
> "perf record" is not successfully started, the sample data PIPE is not ready and we
> get this incompatible file format error.

It'd be great if we can suppress the message.

>
> > >
> > > diff --git a/tools/perf/util/intel-tpebs.c b/tools/perf/util/intel-tpebs.c
> > > index a0585a6571b5..5b8e104f36f1 100644
> > > --- a/tools/perf/util/intel-tpebs.c
> > > +++ b/tools/perf/util/intel-tpebs.c
> > > @@ -263,6 +263,7 @@ int tpebs_start(struct evlist *evsel_list)
> > > }
> > >
> > > if (tpebs_event_size > 0) {
> > > + struct pollfd pollfd = { .events = POLLIN, };
> > > int control_fd[2], ack_fd[2], len;
> > > char ack_buf[8];
> > >
> > > @@ -297,6 +298,19 @@ int tpebs_start(struct evlist *evsel_list)
> > > goto out;
> > > }
> > >
> > > + /* wait for an ack */
> > > + pollfd.fd = ack_fd[0];
> > > +
> > > + if (!poll(&pollfd, 1, 2000)) {
> >
> > Is it 2 seconds? Any specific reason for the value?
> > At least we need a comment to explain the value (or just saying it's a
> > random one).
>
> It's important to have this poll. But the time is random. Please let me know if you have
> any suggestions on the value. Otherwise, I could add a comment saying this is a random
> value.

I don't have a better idea, a comment would be ok.

> >
> >
> > > + pr_err("failed: perf record ack timeout\n");

Can you please prefix the message with "tpebs:"?

> > > + goto out;
> > > + }
> > > +
> > > + if (!(pollfd.revents & POLLIN)) {
> > > + pr_err("failed: did not received an ack\n");

Ditto.

Thanks,
Namhyung

> > > + goto out;
> > > + }
> > > +
> > > ret = read(ack_fd[0], ack_buf, sizeof(ack_buf));
> > > if (ret > 0)
> > > ret = strcmp(ack_buf, "ack\n");
> > >
> > > Thanks,
> > > Weilin

Next message: Athira Rajeev: "Re: [PATCH V6 00/18] Add data type profiling support for powerpc"
Previous message: Baolin Wang: "Re: [PATCH 3/3] mm: shmem: move shmem_huge_global_enabled() into shmem_allowable_huge_orders()"
In reply to: Wang, Weilin: "RE: [RFC PATCH v16 8/8] perf test: Add test for Intel TPEBS counting mode"
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