CoreSight November 2020

coresight@lists.linaro.org

35 participants
45 discussions

by Al Grant

Hi, When using the /cycacc=1/ option the cycle-counting threshold (setting the minimum gap between cycle packets) is set to a default of 256, which is very high and gives poor cycle resolution. Cores can manage far better than this (single digits, if not 1). The threshold can be set lower via sysfs, but it's capped by an ID register which has a (CPU-specific) minimum possible value. Unfortunately on some widely used cores this ID register incorrectly reports 0x100 i.e. 256. The intended value for these cores is 0b100 i.e. 4. The default threshold is rather high and means we don't get as much value out of this feature as we could. In fact, we typically get timestamp packets more often than we get cycle count packets (timestamp packets also have cycle counts, but take up more space in the trace, so it's not the best way to get high resolution cycle counting). The effect of writing a threshold value below what the ID register says, is architecturally unpredictable. So it's not something we can do generally. What I would suggest as the way forward is to: - set the default lower - cap it against the value in the ID register (i.e. the default might be 10, but if the ID register on a given core says 20, program the ETM to 20) - add an event parameter to set the threshold: -e cs_etm/cycacc=1,cycthreshold=10/ - add a 1-bit event parameter to override the checking of the ID register: -e cs_etm/cycacc=1,cycthreshold=10,cycoverride=1/ We could use the CPU errata mechanism to work around the incorrect ID register, but it seems overkill in this case. I'd suggest a default of 8 for the threshold, and 10 bits for the cycthreshold event parameter. If anyone has other ideas, please say. Al

3 years, 5 months

[RFC PATCH] perf session: Fixup timestamp for ordered events

by Leo Yan

Perf tool relies on MMAP/MMAP2 events to prepare DSO maps, it allocates DSO maps for MMAP/MMAP2 events which is used for parsing symbol. Thus, during the recording, perf tool implictly expects the MMAP/MMAP2 events should arrive before AUX event, in other words, MMAP/MMAP2's timestamp should less than AUX event's timestamp, and the MMAP/MMAP2 events will be added into the front of ordered event list; this can allow the DSO maps to be prepared and can be consumed when process AUX event. See the function perf_evlist__prepare_workload(), though it uses pipes to handshake before perf process (the parent process) and forked process for the profiled program, it cannot promise the timing between MMAP/MMAP2 events and AUX event. On Arm Juno board, the AUX event can be observed to arrive ahead than MMAP2 event, with the command: perf record -e cs_etm/@tmc_etr0/ -S -- dd if=/dev/zero of=/dev/null The follow diagram depicts the flow for how the AUX event is arriving ahead than MMAP2 event: T1: T3: T4: perf process Open PMU device Perf is scheduled out; invoke perf_aux_output_end() and generate AUX event ^ ^ ^ | | | CPU0 ---------------------------------------------------> (T) \ \ Forked process is placed on another CPU V CPU1 ---------------------------------------------------> (T) | | V V T2: T5: Invoke execvp() for profiled Record MMAP2 event program In this scenario, the perf main process runs on CPU0 and the profiled program (which is forked child process) runs on CPU1. The main process opens PMU device for AUX trace (T3) and it will generate AUX event until the perf process is scheduled out (T4); the profiled program will be launched by execvp() (T2) and later will record MMAP event for memory mapping (T5). Usually, the AUX event will be later than MMAP2 event, but on the Arm Juno platform, it has chance that AUX event occurs prior to MMAP2 event with two reasons: - Arm Juno platform is big.LITTLE architecture, so CPU0 is big CPU and CPU1 is LITTLE CPU, the performance between big CPU and LITTLE CPU is significant, this gives chance for the perf main process to run much faster than the profiled program; - In the kernel, the RT thread (like kernel's CPUFreq thread) has chance to preempt perf main thread, so when the perf main thread is switched out, the AUX event will be generated and it might be early than profiled program's MMAP2 event. To fix this issue, this patch records the first AUX event's timestamp into 'aux_timestamp', if find any MMAP/MMAP2 event is late coming, it fixes up the MMAP/MMAP2 events' timestamp as 'aux_timestamp-1', so the MMAP/MMAP2 event will be inserted into ordered list ahead than AUX event and also will be handled before AUX event. Signed-off-by: Leo Yan <leo.yan(a)linaro.org> --- tools/perf/util/session.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c index 098080287c68..1aa54941bf81 100644 --- a/tools/perf/util/session.c +++ b/tools/perf/util/session.c @@ -1753,11 +1753,36 @@ static s64 perf_session__process_event(struct perf_session *session, if (tool->ordered_events) { u64 timestamp = -1ULL; + static u64 aux_timestamp = -1ULL; ret = perf_evlist__parse_sample_timestamp(evlist, event, &timestamp); if (ret && ret != -1) return ret; + /* + * Cache the first AUX event's timestamp into 'aux_timestamp', + * which is used to fixup MMAP/MMAP2's timestamp. + */ + if ((event->header.type == PERF_RECORD_AUX) && + (aux_timestamp == -1ULL)) + aux_timestamp = timestamp; + + /* + * If the AUX event arrives prior to MMAP/MMAP2 events, it's + * possible to have no chance to create DSOs when decode AUX + * trace data, thus the symbol cannot be parsed properly. + * To allow the DSOs are prepared before process AUX event, + * fixup the MMAP/MMAP2 events' timestamp to be prior to any + * AUX event's timestamp, so MMAP/MMAP2 events will be + * handled ahead and the DSO map will be prepared before AUX + * event handling. + */ + if (event->header.type == PERF_RECORD_MMAP2 || + event->header.type == PERF_RECORD_MMAP) { + if (timestamp > aux_timestamp) + timestamp = aux_timestamp - 1; + } + ret = perf_session__queue_event(session, event, timestamp, file_offset); if (ret != -ETIME) return ret; -- 2.17.1

3 years, 5 months

Disinfection

by "Diego Sánchez"

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3 years, 5 months

[PATCH stable-5.9 1/2] coresight: etm: perf: Sink selection using sysfs is deprecated

by Linu Cherian

commit bb1860efc817c18fce4112f25f51043e44346d1b upstream. When commit 6d578258b955 ("coresight: Make sysfs functional on topologies with per core sink") was merged to stable, this patch was a pre-requisite and got missed out leading to build breakages. When using the perf interface, sink selection using sysfs is deprecated. Signed-off-by: Linu Cherian <lcherian(a)marvell.com> Signed-off-by: Mathieu Poirier <mathieu.poirier(a)linaro.org> Link: https://lore.kernel.org/r/20200916191737.4001561-14-mathieu.poirier@linaro.… Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org> Reported-by: kernel test robot <lkp(a)intel.com> --- drivers/hwtracing/coresight/coresight-etm-perf.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c index be591b557df9..75379184f391 100644 --- a/drivers/hwtracing/coresight/coresight-etm-perf.c +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c @@ -222,8 +222,6 @@ static void *etm_setup_aux(struct perf_event *event, void **pages, if (event->attr.config2) { id = (u32)event->attr.config2; sink = coresight_get_sink_by_id(id); - } else { - sink = coresight_get_enabled_sink(true); } mask = &event_data->mask; -- 2.25.1

3 years, 5 months

邮件系统升级通知-pwu

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3 years, 5 months

Re: [RFC PATCH v2] coresight: etm4x: Modify core-commit of cpu to avoid the overflow of HiSilicon ETM

by Mathieu Poirier

Hi Liu, On Wed, Aug 19, 2020 at 04:06:37PM +0800, Qi Liu wrote: > When too much trace information is generated on-chip, the ETM will > overflow, and cause data loss. This is a common phenomenon on ETM > devices. > > But sometimes we do not want to lose performance trace data, so we > suppress the speed of instructions sent from CPU core to ETM to > avoid the overflow of ETM. > > Signed-off-by: Qi Liu <liuqi115(a)huawei.com> > --- > > Changes since v1: > - ETM on HiSilicon Hip09 platform supports backpressure, so does > not need to modify core commit. > > drivers/hwtracing/coresight/coresight-etm4x.c | 43 +++++++++++++++++++++++++++ > 1 file changed, 43 insertions(+) > > diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c > index 7797a57..7641f89 100644 > --- a/drivers/hwtracing/coresight/coresight-etm4x.c > +++ b/drivers/hwtracing/coresight/coresight-etm4x.c > @@ -43,6 +43,10 @@ MODULE_PARM_DESC(boot_enable, "Enable tracing on boot"); > #define PARAM_PM_SAVE_NEVER 1 /* never save any state */ > #define PARAM_PM_SAVE_SELF_HOSTED 2 /* save self-hosted state only */ > > +#define CORE_COMMIT_CLEAR 0x3000 > +#define CORE_COMMIT_SHIFT 12 > +#define HISI_ETM_AMBA_ID_V1 0x000b6d01 > + > static int pm_save_enable = PARAM_PM_SAVE_FIRMWARE; > module_param(pm_save_enable, int, 0444); > MODULE_PARM_DESC(pm_save_enable, > @@ -104,11 +108,40 @@ struct etm4_enable_arg { > int rc; > }; > > +static void etm4_cpu_actlr1_cfg(void *info) > +{ > + struct etm4_enable_arg *arg = (struct etm4_enable_arg *)info; > + u64 val; > + > + asm volatile("mrs %0,s3_1_c15_c2_5" : "=r"(val)); > + val &= ~CORE_COMMIT_CLEAR; > + val |= arg->rc << CORE_COMMIT_SHIFT; > + asm volatile("msr s3_1_c15_c2_5,%0" : : "r"(val)); > +} > + > +static void etm4_config_core_commit(int cpu, int val) > +{ > + struct etm4_enable_arg arg = {0}; > + > + arg.rc = val; > + smp_call_function_single(cpu, etm4_cpu_actlr1_cfg, &arg, 1); Function etm4_enable/disable_hw() are already running on the CPU they are supposed to so no need to call smp_call_function_single(). > +} > + > static int etm4_enable_hw(struct etmv4_drvdata *drvdata) > { > int i, rc; > + struct amba_device *adev; > struct etmv4_config *config = &drvdata->config; > struct device *etm_dev = &drvdata->csdev->dev; > + struct device *dev = drvdata->csdev->dev.parent; > + > + adev = container_of(dev, struct amba_device, dev); > + /* > + * If ETM device is HiSilicon ETM device, reduce the > + * core-commit to avoid ETM overflow. > + */ > + if (adev->periphid == HISI_ETM_AMBA_ID_V1) Do you have any documentation on this back pressure feature? I doubt this is specific to Hip09 platform and as such would prefer to have a more generic approach that works on any platform that supports it. Anyone on the CS mailing list that knows what this is about? Thanks, Mathieu > + etm4_config_core_commit(drvdata->cpu, 1); > > CS_UNLOCK(drvdata->base); > > @@ -472,10 +505,20 @@ static void etm4_disable_hw(void *info) > { > u32 control; > struct etmv4_drvdata *drvdata = info; > + struct device *dev = drvdata->csdev->dev.parent; > struct etmv4_config *config = &drvdata->config; > struct device *etm_dev = &drvdata->csdev->dev; > + struct amba_device *adev; > int i; > > + adev = container_of(dev, struct amba_device, dev); > + /* > + * If ETM device is HiSilicon ETM device, resume the > + * core-commit after ETM trace is complete. > + */ > + if (adev->periphid == HISI_ETM_AMBA_ID_V1) > + etm4_config_core_commit(drvdata->cpu, 0); > + > CS_UNLOCK(drvdata->base); > > if (!drvdata->skip_power_up) { > -- > 2.8.1 >

3 years, 5 months

[PATCH v4 0/2] Make sysFS functional on topologies with per core sink

by Linu Cherian

This patch series tries to fix the sysfs breakage on topologies with per core sink. Changes since v3: - References to coresight_get_enabled_sink in perf interface has been removed and marked deprecated as a new patch. - To avoid changes to coresight_find_sink for ease of maintenance, search function specific to sysfs usage has been added. - Sysfs being the only user for coresight_get_enabled sink, reset option is removed as well. Changes since v2: - Fixed checkpatch issue Changes since v1: - Misc fixes in commit message Applies on https://git.linaro.org/kernel/coresight.git/log/?h=next Linu Cherian (2): coresight: etm: perf: Sink selection using sysfs is deprecated coresight: Make sysFS functional on topologies with per core sink .../hwtracing/coresight/coresight-etm-perf.c | 2 - drivers/hwtracing/coresight/coresight-priv.h | 3 +- drivers/hwtracing/coresight/coresight.c | 58 +++++++++---------- 3 files changed, 29 insertions(+), 34 deletions(-) base-commit: 17f17c8f02a35a746376c2ecd054386575835b8b -- 2.25.1

3 years, 5 months

perf cs-etm: Multi-thread support

by Andrea Brunato

Good morning, Is tracing a multi-threaded program a supported use case for perf cs-etm? If yes, are there any flags that should be specified with perf? Thanks, Andrea IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.

3 years, 5 months

Invitation to Research Design, ODK mobile data collection, GIS data mapping, Data analysis using NVIVO and R training

by FDC Training

3 years, 5 months

[PATCH RESEND 1/2] perf test: Fix a typo in cs-etm testing

by Leo Yan

Fix a typo: s/devce_name/device_name. Fixes: fe0aed19b266 ("perf test: Introduce script for Arm CoreSight testing") Signed-off-by: Leo Yan <leo.yan(a)linaro.org> --- Resend patches for adding "Fixes" tags. tools/perf/tests/shell/test_arm_coresight.sh | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/perf/tests/shell/test_arm_coresight.sh b/tools/perf/tests/shell/test_arm_coresight.sh index 8d84fdbed6a6..59d847d4981d 100755 --- a/tools/perf/tests/shell/test_arm_coresight.sh +++ b/tools/perf/tests/shell/test_arm_coresight.sh @@ -105,7 +105,7 @@ arm_cs_iterate_devices() { # `> device_name = 'tmc_etf0' device_name=$(basename $path) - if is_device_sink $path $devce_name; then + if is_device_sink $path $device_name; then record_touch_file $device_name $2 && perf_script_branch_samples touch && -- 2.17.1

3 years, 5 months

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CoreSight November 2020