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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=qRSqkUf+llYU4VO85zANUOiRZ8w9zyh0JSFN1AoMWgU=; b=fGlQONVAcPhhd8ANVBdO11twfQIGS4rW9SyM1VRtKyclAAUcaG9fTyipTMH8N1KQfY Nl65u5HyXF3NBYzqQ/x8pDqWyRHlwLL+5n1uqs+GHau7JqAhqxlkG3DEJWIkV7cC8PdX hDO+uNkSHU9UssqCBKWzAhw5AyFK9+VfkdKqSlygD6dTlakv3TtdiLG7MJ0ByiF1QZpW PwiM2Ef23P10nWUZtohgMjB1nQ9cG36om9POK3t7A0J/dWK2FwQoHOL/WmWao+7i796y WH0vRe9XFqrlDxXNZy92Chl91nDrNVCigebBiDZXqbHXZ1oBmqVJsSKcgTjwFFYOl4zB 1YGg== X-Gm-Message-State: APjAAAWDOaNJ0S9Ewxh33E6aDYdrxYcwTzoPbUwLDMJFWQ/f1F4nbQaO ax49h0Wk02gGLf73fJFIWpGJQpaJiHBKO+3ECf8Ggw== X-Google-Smtp-Source: APXvYqx2EqsSxBrbcEbmUgONTOe+kK6NPuSxxRx6QbmAxakVCHiJ4zE+CU+DQaU/vZwavRuisclhEK3YuQ0DAIUC+40= X-Received: by 2002:a5d:9e01:: with SMTP id h1mr1500956ioh.57.1558382021049; Mon, 20 May 2019 12:53:41 -0700 (PDT) MIME-Version: 1.0 References: <20190514194018.23420-1-mathieu.poirier@linaro.org> <20190514194018.23420-7-mathieu.poirier@linaro.org> <20190516150005.GG12557@leoy-ThinkPad-X240s> In-Reply-To: <20190516150005.GG12557@leoy-ThinkPad-X240s> From: Mathieu Poirier Date: Mon, 20 May 2019 13:53:29 -0600 Message-ID: Subject: Re: [PATCH V2 6/6] perf tools: Properly set the value of 'old' and 'head' in snapshot mode To: Leo Yan X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190520_125345_971602_85517144 X-CRM114-Status: GOOD ( 30.35 ) 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 K. Poulose" , Alexander Shishkin , Coresight ML , Arnaldo Carvalho de Melo , Peter Zijlstra , Ingo Molnar , linux-arm-kernel , Mike Leach 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 Thu, 16 May 2019 at 09:00, Leo Yan wrote: > > 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]) > It would be if buf[] was a char *, but it is a u64 *. > 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