RE: [PATCH v2 0/7] perf arm-spe: Enable timestamp

[Al Grant]

> -----Original Message-----
> From: Leo Yan <leo.yan@xxxxxxxxxx>
> Sent: 03 April 2021 08:24
> To: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>; John Garry
> <john.garry@xxxxxxxxxx>; Will Deacon <will@xxxxxxxxxx>; Mathieu Poirier
> <mathieu.poirier@xxxxxxxxxx>; James Clark <James.Clark@xxxxxxx>; Al Grant
> <Al.Grant@xxxxxxx>; Peter Zijlstra <peterz@xxxxxxxxxxxxx>; Ingo Molnar
> <mingo@xxxxxxxxxx>; Mark Rutland <Mark.Rutland@xxxxxxx>; Alexander
> Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>; Jiri Olsa <jolsa@xxxxxxxxxx>;
> Namhyung Kim <namhyung@xxxxxxxxxx>; Adrian Hunter
> <adrian.hunter@xxxxxxxxx>; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx
> Cc: leo.yan@xxxxxxxxxx
> Subject: [PATCH v2 0/7] perf arm-spe: Enable timestamp
> 
> As we know, the timestamp is important for AUX trace; it's mainly used to
> correlate between perf events and AUX trace, allows to generate events with
> time ordered manner.  There have several good examples of enabling timestamp
> for AUX trace (like Intel-pt, Intel-bts, etc).
> 
> Since the conversion between TSC and kernel timestamp has been supported on
> Arm64, TSC is a naming convention from x86, but perf now has reused it to
> support Arm arch timer counter.
> 
> This patch set is to enable timestamp for Arm SPE trace.  It reads out TSC
> parameters from mmap page and stores into auxtrace info structure;

Why not synthesize a PERF_RECORD_TIME_CONV - isn't that specifically to
capture the TSC parameters from the mmap page? If a generic mechanism
exists it would be better to use it, otherwise we'll have to do this again for
future trace formats.

perf_read_tsc_conversion and perf_event__synth_time_conv are currently
in arch/x86/util/tsc.c, but nothing in them is x86-specific and they could be
moved somewhere more generic.

Al


> the TSC
> parameters are used for conversion between timer counter and kernel time and
> which is applied for Arm SPE samples.
> 
> This patch set can be clearly applied on perf/core branch with:
> 
>   commit 6859bc0e78c6 ("perf stat: Improve readability of shadow stats")
> 
> Ths patch series has been tested on Hisilicon D06 platform.
> 
> After:
> 
>   # perf script -F comm,time,cpu,pid,dso,ip,sym
> 
>               perf  2408 [032]   168.680297:  ffffbd1253690a3c perf_event_exec
> ([kernel.kallsyms])
>               perf  2408 [032]   168.680297:  ffffbd1253690a3c perf_event_exec
> ([kernel.kallsyms])
>    false_sharing.e  2408 [032]   168.680317:  ffffbd1253683f50
> perf_iterate_ctx.constprop.0 ([kernel.kallsyms])
>    false_sharing.e  2408 [032]   168.680317:  ffffbd1253683f50
> perf_iterate_ctx.constprop.0 ([kernel.kallsyms])
>    false_sharing.e  2408 [032]   168.680319:  ffffbd1253683f70
> perf_iterate_ctx.constprop.0 ([kernel.kallsyms])
>    false_sharing.e  2408 [032]   168.680319:  ffffbd1253683f70
> perf_iterate_ctx.constprop.0 ([kernel.kallsyms])
>    false_sharing.e  2408 [032]   168.680367:  ffffbd12539b03ec
> __arch_clear_user ([kernel.kallsyms])
>    false_sharing.e  2408 [032]   168.680375:  ffffbd1253721440
> kmem_cache_alloc ([kernel.kallsyms])
>    false_sharing.e  2408 [032]   168.680375:  ffffbd1253721440
> kmem_cache_alloc ([kernel.kallsyms])
>    false_sharing.e  2408 [032]   168.680375:  ffffbd1253721440
> kmem_cache_alloc ([kernel.kallsyms])
>    false_sharing.e  2408 [032]   168.680375:  ffffbd1253721440
> kmem_cache_alloc ([kernel.kallsyms])
>    false_sharing.e  2408 [032]   168.680376:  ffffbd1253683f70
> perf_iterate_ctx.constprop.0 ([kernel.kallsyms])
>    false_sharing.e  2408 [032]   168.680376:  ffffbd1253683f70
> perf_iterate_ctx.constprop.0 ([kernel.kallsyms])
>    false_sharing.e  2408 [032]   168.680376:  ffffbd1253683f70
> perf_iterate_ctx.constprop.0 ([kernel.kallsyms])
> 
> Changes from v1:
> * Rebased patch series on the latest perf/core branch;
> * Fixed the patch for dumping TSC parameters to support both the
>   older and new auxtrace info format.
> 
> 
> Leo Yan (7):
>   perf arm-spe: Remove unused enum value ARM_SPE_PER_CPU_MMAPS
>   perf arm-spe: Store TSC parameters in auxtrace info
>   perf arm-spe: Dump TSC parameters
>   perf arm-spe: Convert event kernel time to counter value
>   perf arm-spe: Assign kernel time to synthesized event
>   perf arm-spe: Bail out if the trace is later than perf event
>   perf arm-spe: Don't wait for PERF_RECORD_EXIT event
> 
>  tools/perf/arch/arm64/util/arm-spe.c | 23 +++++++
>  tools/perf/util/arm-spe.c            | 89 +++++++++++++++++++++++-----
>  tools/perf/util/arm-spe.h            |  7 ++-
>  3 files changed, 103 insertions(+), 16 deletions(-)
> 
> --
> 2.25.1