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[50.116.44.211]) by smtp.gmail.com with ESMTPSA id m3sm1891302ywf.39.2019.05.16.08.00.10 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 16 May 2019 08:00:13 -0700 (PDT) Date: Thu, 16 May 2019 23:00:05 +0800 From: Leo Yan To: Mathieu Poirier Subject: Re: [PATCH V2 6/6] perf tools: Properly set the value of 'old' and 'head' in snapshot mode Message-ID: <20190516150005.GG12557@leoy-ThinkPad-X240s> References: <20190514194018.23420-1-mathieu.poirier@linaro.org> <20190514194018.23420-7-mathieu.poirier@linaro.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190514194018.23420-7-mathieu.poirier@linaro.org> User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190516_080016_666364_6A804837 X-CRM114-Status: GOOD ( 28.19 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: suzuki.poulose@arm.com, alexander.shishkin@linux.intel.com, coresight@lists.linaro.org, acme@kernel.org, peterz@infradead.org, mingo@redhat.com, linux-arm-kernel@lists.infradead.org, mike.leach@linaro.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, May 14, 2019 at 01:40:18PM -0600, Mathieu Poirier wrote: > This patch adds the necessay intelligence to properly compute the value > of 'old' and 'head' when operating in snapshot mode. That way we can get > the latest information in the AUX buffer and be compatible with the > generic AUX ring buffer mechanic. > > Signed-off-by: Mathieu Poirier > --- > tools/perf/arch/arm/util/cs-etm.c | 124 ++++++++++++++++++++++++++++-- > 1 file changed, 119 insertions(+), 5 deletions(-) > > diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c > index 911426721170..3734e3fd18f8 100644 > --- a/tools/perf/arch/arm/util/cs-etm.c > +++ b/tools/perf/arch/arm/util/cs-etm.c > @@ -31,6 +31,8 @@ struct cs_etm_recording { > struct auxtrace_record itr; > struct perf_pmu *cs_etm_pmu; > struct perf_evlist *evlist; > + int wrapped_cnt; > + bool *wrapped; > bool snapshot_mode; > size_t snapshot_size; > }; > @@ -536,16 +538,126 @@ static int cs_etm_info_fill(struct auxtrace_record *itr, > return 0; > } > > -static int cs_etm_find_snapshot(struct auxtrace_record *itr __maybe_unused, > +static int cs_etm_alloc_wrapped_array(struct cs_etm_recording *ptr, int idx) > +{ > + bool *wrapped; > + int cnt = ptr->wrapped_cnt; > + > + /* Make @ptr->wrapped as big as @idx */ > + while (cnt <= idx) > + cnt++; > + > + /* Free'ed in cs_etm_recording_free() */ > + wrapped = reallocarray(ptr->wrapped, cnt, sizeof(bool)); > + if (!wrapped) > + return -ENOMEM; > + > + ptr->wrapped_cnt = cnt; > + ptr->wrapped = wrapped; > + > + return 0; > +} > + > +static bool cs_etm_buffer_has_wrapped(unsigned char *buffer, > + size_t buffer_size, u64 head) > +{ > + u64 i, watermark; > + u64 *buf = (u64 *)buffer; > + size_t buf_size = buffer_size; > + > + /* > + * We want to look the very last 512 byte (chosen arbitrarily) in > + * the ring buffer. > + */ > + watermark = buf_size - 512; > + > + /* > + * @head is continuously increasing - if its value is equal or greater > + * than the size of the ring buffer, it has wrapped around. > + */ > + if (head >= buffer_size) > + return true; > + > + /* > + * The value of @head is somewhere within the size of the ring buffer. > + * This can be that there hasn't been enough data to fill the ring > + * buffer yet or the trace time was so long that @head has numerically > + * wrapped around. To find we need to check if we have data at the very > + * end of the ring buffer. We can reliably do this because mmap'ed > + * pages are zeroed out and there is a fresh mapping with every new > + * session. > + */ > + > + /* @head is less than 512 byte from the end of the ring buffer */ > + if (head > watermark) > + watermark = head; > + > + /* > + * Speed things up by using 64 bit transactions (see "u64 *buf" above) > + */ > + watermark >>= 3; > + buf_size >>= 3; > + > + /* > + * If we find trace data at the end of the ring buffer, @head has > + * been there and has numerically wrapped around at least once. > + */ > + for (i = watermark; i < buf_size; i++) > + if (buf[i]) I think here should be: if (buf[i << 3]) Otherwise, this patch looks good to me. > + return true; > + > + return false; > +} > + > +static int cs_etm_find_snapshot(struct auxtrace_record *itr, > int idx, struct auxtrace_mmap *mm, > - unsigned char *data __maybe_unused, > + unsigned char *data, > u64 *head, u64 *old) > { > - pr_debug3("%s: mmap index %d old head %zu new head %zu size %zu\n", > + int err; > + bool wrapped; > + struct cs_etm_recording *ptr = > + container_of(itr, struct cs_etm_recording, itr); > + > + /* > + * Allocate memory to keep track of wrapping if this is the first > + * time we deal with this *mm. > + */ > + if (idx >= ptr->wrapped_cnt) { > + err = cs_etm_alloc_wrapped_array(ptr, idx); > + if (err) > + return err; > + } > + > + /* > + * Check to see if *head has wrapped around. If it hasn't only the > + * amount of data between *head and *old is snapshot'ed to avoid > + * bloating the perf.data file with zeros. But as soon as *head has > + * wrapped around the entire size of the AUX ring buffer it taken. > + */ > + wrapped = ptr->wrapped[idx]; > + if (!wrapped && cs_etm_buffer_has_wrapped(data, mm->len, *head)) { > + wrapped = true; > + ptr->wrapped[idx] = true; > + } > + > + pr_debug3("%s: mmap index %d old head %lx new head %lx size %lx\n", > __func__, idx, (size_t)*old, (size_t)*head, mm->len); > > - *old = *head; > - *head += mm->len; > + /* No wrap has occurred, we can just use *head and *old. */ > + if (!wrapped) > + return 0; > + > + /* > + * *head has wrapped around - adjust *head and *old to pickup the > + * entire content of the AUX buffer. > + */ > + if (*head >= mm->len) { > + *old = *head - mm->len; > + } else { > + *head += mm->len; > + *old = *head - mm->len; > + } > > return 0; > } > @@ -586,6 +698,8 @@ static void cs_etm_recording_free(struct auxtrace_record *itr) > { > struct cs_etm_recording *ptr = > container_of(itr, struct cs_etm_recording, itr); > + > + zfree(&ptr->wrapped); > free(ptr); > } > > -- > 2.17.1 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel