Re: [PATCH v2 0/9] jevents/pmu-events improvements

[John Garry]

On 21/12/2022 22:34, Ian Rogers wrote:
> Add an optimization to jevents using the metric code, rewrite metrics
> in terms of each other in order to minimize size and improve
> readability. For example, on Power8
> other_stall_cpi is rewritten from:
> "PM_CMPLU_STALL / PM_RUN_INST_CMPL - PM_CMPLU_STALL_BRU_CRU / PM_RUN_INST_CMPL - PM_CMPLU_STALL_FXU / PM_RUN_INST_CMPL - PM_CMPLU_STALL_VSU / PM_RUN_INST_CMPL - PM_CMPLU_STALL_LSU / PM_RUN_INST_CMPL - PM_CMPLU_STALL_NTCG_FLUSH / PM_RUN_INST_CMPL - PM_CMPLU_STALL_NO_NTF / PM_RUN_INST_CMPL"
> to:
> "stall_cpi - bru_cru_stall_cpi - fxu_stall_cpi - vsu_stall_cpi - lsu_stall_cpi - ntcg_flush_cpi - no_ntf_stall_cpi"
> Which more closely matches the definition on Power9.
>
> A limitation of the substitutions are that they depend on strict
> equality and the shape of the tree. This means that for "a + b + c"
> then a substitution of "a + b" will succeed while "b + c" will fail
> (the LHS for "+ c" is "a + b" not just "b").
>
> Separate out the events and metrics in the pmu-events tables saving
> 14.8% in the table size while making it that metrics no longer need to
> iterate over all events and vice versa. These changes remove evsel's
> direct metric support as the pmu_event no longer has a metric to
> populate it. This is a minor issue as the code wasn't working
> properly, metrics for this are rare and can still be properly ran
> using '-M'.
>
> Add an ability to just build certain models into the jevents generated
> pmu-metrics.c code. This functionality is appropriate for operating
> systems like ChromeOS, that aim to minimize binary size and know all
> the target CPU models.

From a glance, this does not look like it would work for arm64. As I 
see in the code, we check the model in the arch folder for the test to 
see if built. For arm64, as it uses arch/implementator/model folder org, 
and not just arch/model (like x86)

So on the assumption that it does not work for arm64 (or just any arch 
which uses arch/implementator/model folder org), it would be nice to 
have that feature also. Or maybe also support not just specifying model 
but also implementator.

> v2. Rebase. Modify the code that skips rewriting a metric with the
>      same name with itself, to make the name check case insensitive.


Unfortunately you might need another rebase as this does not apply to 
acme perf/core (if that is what you want), now for me at:

5670ebf54bd2 (HEAD, origin/tmp.perf/core, origin/perf/core, perf/core)
perf cs-etm: Ensure that Coresight timestamps don't go backwards

> Ian Rogers (9):
>    perf jevents metric: Correct Function equality
>    perf jevents metric: Add ability to rewrite metrics in terms of others
>    perf jevents: Rewrite metrics in the same file with each other
>    perf pmu-events: Separate metric out of pmu_event
>    perf stat: Remove evsel metric_name/expr
>    perf jevents: Combine table prefix and suffix writing
>    perf pmu-events: Introduce pmu_metrics_table
>    perf jevents: Generate metrics and events as separate tables
>    perf jevents: Add model list option

Thanks,
John