Messages in this thread | | | Subject | Re: [PATCH 0/4] TopDown metrics support for Ice Lake (perf tool) | From | "Liang, Kan" <> | Date | Thu, 27 Aug 2020 08:39:39 -0400 |
| |
On 8/26/2020 11:54 AM, Jiri Olsa wrote: > On Thu, Aug 20, 2020 at 09:45:28AM -0700, kan.liang@linux.intel.com wrote: >> From: Kan Liang <kan.liang@linux.intel.com> >> >> The kernel patches have been merged into the tip's perf/core branch. >> The patch set is on top of commit 2cb5383b30d4 ("perf/x86/intel: Support >> per-thread RDPMC TopDown metrics") of the tip's perf/core branch. >> >> The changes for the perf tool include: >> - Extend --topdown option to support per thread TopDown metrics >> - Support sample-read topdown metric group >> - Add a complete document for the TopDown usage. >> >> Ice Lake has support for measuring the level 1 TopDown metrics >> directly in hardware. This is implemented by an additional METRICS >> register, and a new Fixed Counter 3 that measures pipeline SLOTS. >> >> New in Icelake >> - Do not require generic counters. This allows to collect TopDown always >> in addition to other events. >> - Measuring TopDown per thread/process instead of only per core >> >> For the Ice Lake implementation of performance metrics, the values in >> PERF_METRICS MSR are derived from fixed counter 3. Software should start >> both registers, PERF_METRICS and fixed counter 3, from zero. >> Additionally, software is recommended to periodically clear both >> registers in order to maintain accurate measurements. The latter is >> required for certain scenarios that involve sampling metrics at high >> rates. Software should always write fixed counter 3 before write to >> PERF_METRICS. >> >> IA32_PERF_GLOBAL_STATUS. OVF_PERF_METRICS[48]: If this bit is set, >> it indicates that some PERF_METRICS-related counter has overflowed and >> a PMI is triggered. Software has to synchronize, e.g. re-start, >> PERF_METRICS as well as fixed counter 3. Otherwise, PERF_METRICS may >> return invalid values. >> >> Limitation >> - To get accurate result and avoid reading the METRICS register multiple >> times, the TopDown metrics events and SLOTS event have to be in the >> same group. >> - METRICS and SLOTS registers have to be cleared after each read by SW. >> That is to prevent the lose of precision. >> - Cannot do sampling read SLOTS and TopDown metric events >> >> Please refer SDM Vol3, 18.3.9.3 Performance Metrics for the details of >> TopDown metrics. >> >> Andi Kleen (2): >> perf stat: Support new per thread TopDown metrics >> perf, tools: Add documentation for topdown metrics >> >> Kan Liang (2): >> perf tools: Rename group to topdown >> perf record: Support sample-read topdown metric group > > I don't have Ice lake to actualy check, but it looks good > > Acked-by: Jiri Olsa <jolsa@redhat.com> >
Thanks Jirka for the review.
Hi Arnaldo,
Andi has a comment regarding a grammar error in the printf message. I once plan to apply a fix in the next version. I'm not sure whether you will have more comments for this patch set. If yes, I will wait for the comments. If not, should I send a V2 patch set with this fixed?
On 8/20/2020 4:05 PM, Andi Kleen wrote: >> + fprintf(stat_config.output, >> + "Topdown accuracy may decreases when measuring long period.\n" > "may decrease" ... "long periods". > > (s needs to move to the end)
Thanks, Kan
| |