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[68.147.0.187]) by smtp.gmail.com with ESMTPSA id d6sm2778016pfn.197.2021.04.15.12.54.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Apr 2021 12:54:18 -0700 (PDT) Date: Thu, 15 Apr 2021 13:54:16 -0600 From: Mathieu Poirier To: James Clark Cc: coresight@lists.linaro.org, al.grant@arm.com, branislav.rankov@arm.com, denik@chromium.org, suzuki.poulose@arm.com, Mike Leach , Leo Yan , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , John Garry , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] perf cs-etm: Set time on synthesised samples to preserve ordering Message-ID: <20210415195416.GB937505@xps15> References: <20210414143919.12605-1-james.clark@arm.com> <20210414143919.12605-2-james.clark@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210414143919.12605-2-james.clark@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 14, 2021 at 05:39:19PM +0300, James Clark wrote: > The following attribute is set when synthesising samples in > timed decoding mode: > > attr.sample_type |= PERF_SAMPLE_TIME; > > This results in new samples that appear to have timestamps but > because we don't assign any timestamps to the samples, when the > resulting inject file is opened again, the synthesised samples > will be on the wrong side of the MMAP or COMM events. > I understand the problem. Once again an issue caused by CS and the kernel having a different view of time. > For example this results in the samples being associated with > the perf binary, rather than the target of the record: > > perf record -e cs_etm/@tmc_etr0/u top > perf inject -i perf.data -o perf.inject --itrace=i100il > perf report -i perf.inject > > Where 'Command' == perf should show as 'top': > > # Overhead Command Source Shared Object Source Symbol Target Symbol Basic Block Cycles > # ........ ....... .................... ...................... ...................... .................. > # > 31.08% perf [unknown] [.] 0x000000000040c3f8 [.] 0x000000000040c3e8 - > > If the perf.data file is opened directly with perf, without the > inject step, then this already works correctly because the > events are synthesised after the COMM and MMAP events and > no second sorting happens. Re-sorting only happens when opening > the perf.inject file for the second time so timestamps are > needed. > > Using the timestamp from the AUX record mirrors the current > behaviour when opening directly with perf, because the events > are generated on the call to cs_etm__process_queues(). > > Signed-off-by: James Clark > Co-developed-by: Al Grant > Signed-off-by: Al Grant Suzuki is correct, your name has to appear after Al's. > --- > tools/perf/util/cs-etm.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c > index c25da2ffa8f3..d0fa9dce47f1 100644 > --- a/tools/perf/util/cs-etm.c > +++ b/tools/perf/util/cs-etm.c > @@ -54,6 +54,7 @@ struct cs_etm_auxtrace { > u8 sample_instructions; > > int num_cpu; > + u64 latest_kernel_timestamp; > u32 auxtrace_type; > u64 branches_sample_type; > u64 branches_id; > @@ -1192,6 +1193,8 @@ static int cs_etm__synth_instruction_sample(struct cs_etm_queue *etmq, > event->sample.header.misc = cs_etm__cpu_mode(etmq, addr); > event->sample.header.size = sizeof(struct perf_event_header); > > + if (!etm->timeless_decoding) > + sample.time = etm->latest_kernel_timestamp; > sample.ip = addr; > sample.pid = tidq->pid; > sample.tid = tidq->tid; > @@ -1248,6 +1251,8 @@ static int cs_etm__synth_branch_sample(struct cs_etm_queue *etmq, > event->sample.header.misc = cs_etm__cpu_mode(etmq, ip); > event->sample.header.size = sizeof(struct perf_event_header); > > + if (!etm->timeless_decoding) > + sample.time = etm->latest_kernel_timestamp; > sample.ip = ip; > sample.pid = tidq->pid; > sample.tid = tidq->tid; > @@ -2412,9 +2417,10 @@ static int cs_etm__process_event(struct perf_session *session, > else if (event->header.type == PERF_RECORD_SWITCH_CPU_WIDE) > return cs_etm__process_switch_cpu_wide(etm, event); > > - if (!etm->timeless_decoding && > - event->header.type == PERF_RECORD_AUX) > + if (!etm->timeless_decoding && event->header.type == PERF_RECORD_AUX) { > + etm->latest_kernel_timestamp = sample_kernel_timestamp; It will be fun to fix this when 8.4 comes out but for now it's the best we've got. Reviewed-by: Mathieu Poirier > return cs_etm__process_queues(etm); > + } > > return 0; > } > -- > 2.28.0 >