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[45.79.108.178]) by smtp.gmail.com with ESMTPSA id u15sm4893693pju.44.2021.05.12.08.23.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 May 2021 08:23:37 -0700 (PDT) Date: Wed, 12 May 2021 23:23:30 +0800 From: Leo Yan To: James Clark Cc: Arnaldo Carvalho de Melo , John Garry , Will Deacon , Mathieu Poirier , Peter Zijlstra , Ingo Molnar , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , linux-arm-kernel@lists.infradead.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, Al Grant Subject: Re: [PATCH v1 2/3] perf arm-spe: Correct sample flags for dummy event Message-ID: <20210512152330.GA121227@leoy-ThinkPad-X240s> References: <20210429150100.282180-1-leo.yan@linaro.org> <20210429150100.282180-3-leo.yan@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-perf-users@vger.kernel.org On Wed, May 12, 2021 at 05:39:56PM +0300, James Clark wrote: > > > On 29/04/2021 18:00, Leo Yan wrote: > > The dummy event is mainly used for mmap, the TIME sample is only needed > > for per-cpu case so that the perf tool can rely on the correct timing > > for parsing symbols. And the CPU sample is useless for mmap. > > > > This patch enables TIME sample for per-cpu mmap and doesn't enable CPU > > sample. For later extension (e.g. support multiple AUX events), it sets > > the dummy event when the condition "opts->full_auxtrace" is true. > > > > Signed-off-by: Leo Yan > > --- > > tools/perf/arch/arm64/util/arm-spe.c | 30 ++++++++++++++++------------ > > 1 file changed, 17 insertions(+), 13 deletions(-) > > > > diff --git a/tools/perf/arch/arm64/util/arm-spe.c b/tools/perf/arch/arm64/util/arm-spe.c > > index 902e73a64184..f6eec0900604 100644 > > --- a/tools/perf/arch/arm64/util/arm-spe.c > > +++ b/tools/perf/arch/arm64/util/arm-spe.c > > @@ -70,7 +70,6 @@ static int arm_spe_recording_options(struct auxtrace_record *itr, > > struct evsel *evsel, *arm_spe_evsel = NULL; > > struct perf_cpu_map *cpus = evlist->core.cpus; > > bool privileged = perf_event_paranoid_check(-1); > > - struct evsel *tracking_evsel; > > int err; > > > > sper->evlist = evlist; > > @@ -126,18 +125,23 @@ static int arm_spe_recording_options(struct auxtrace_record *itr, > > evsel__set_sample_bit(arm_spe_evsel, CPU); > > > > /* Add dummy event to keep tracking */ > > - err = parse_events(evlist, "dummy:u", NULL); > > - if (err) > > - return err; > > - > > - tracking_evsel = evlist__last(evlist); > > - evlist__set_tracking_event(evlist, tracking_evsel); > > - > > - tracking_evsel->core.attr.freq = 0; > > - tracking_evsel->core.attr.sample_period = 1; > > - evsel__set_sample_bit(tracking_evsel, TIME); > > - evsel__set_sample_bit(tracking_evsel, CPU); > > - evsel__reset_sample_bit(tracking_evsel, BRANCH_STACK); > > + if (opts->full_auxtrace) { > > + struct evsel *tracking_evsel; > > Hi Leo, > > I know the "if (opts->full_auxtrace)" pattern is copied from other auxtrace > files, but I don't think it does anything because there is this at the top > of the function: > > if (!opts->full_auxtrace) > return 0; > > The same applies for other usages of "full_auxtrace" in the same function. > They are all always true. I'm also not sure if it's ever defined what > full_auxtrace means. Good pointing. TBH, I also stuggled for handling "opts->full_auxtrace" when wrote the patch; IIUC, "opts->full_auxtrace" is also used in builtin-record.c to indicate if the recording contains AUX tracing. Will follow your suggestion to respin the patch (and refine the code) to remove the redundant condition checking for "opts->full_auxtrace". Thanks, Leo