Re: [PATCH v9 00/13] Don't compute events that won't be used in a metric.

[PATCH v9 00/13] Don't compute events that won't be used in a metric. · Ian Rogers <irogers@google.com> · 2021-09-23
[PATCH v9 01/13] perf metric: Restructure struct expr_parse_ctx. · Ian Rogers <irogers@google.com> · 2021-09-23
[PATCH v9 02/13] perf metric: Use NAN for missing event IDs. · Ian Rogers <irogers@google.com> · 2021-09-23
[PATCH v9 03/13] perf expr: Remove unused headers and inline d_ratio · Ian Rogers <irogers@google.com> · 2021-09-23
[PATCH v9 04/13] perf expr: Separate token declataion from type · Ian Rogers <irogers@google.com> · 2021-09-23
[PATCH v9 05/13] perf expr: Use macros for operators · Ian Rogers <irogers@google.com> · 2021-09-23
[PATCH v9 06/13] perf expr: Move actions to the left. · Ian Rogers <irogers@google.com> · 2021-09-23
[PATCH v9 07/13] perf metric: Rename expr__find_other. · Ian Rogers <irogers@google.com> · 2021-09-23
[PATCH v9 08/13] perf metric: Add utilities to work on ids map. · Ian Rogers <irogers@google.com> · 2021-09-23
[PATCH v9 09/13] perf metric: Allow metrics with no events · Ian Rogers <irogers@google.com> · 2021-09-23
[PATCH v9 10/13] perf expr: Merge find_ids and regular parsing · Ian Rogers <irogers@google.com> · 2021-09-23
Re: [PATCH v9 10/13] perf expr: Merge find_ids and regular parsing · Jiri Olsa <hidden> · 2021-09-28
Re: [PATCH v9 10/13] perf expr: Merge find_ids and regular parsing · Ian Rogers <irogers@google.com> · 2021-09-28
[PATCH v9 12/13] perf metric: Don't compute unused events · Ian Rogers <irogers@google.com> · 2021-09-23
[PATCH v9 11/13] perf expr: Propagate constants for binary operations · Ian Rogers <irogers@google.com> · 2021-09-23
[PATCH v9 13/13] perf metric: Avoid events for an 'if' constant result · Ian Rogers <irogers@google.com> · 2021-09-23
Re: [PATCH v9 00/13] Don't compute events that won't be used in a metric. · Jiri Olsa <hidden> · 2021-09-29
Re: [PATCH v9 00/13] Don't compute events that won't be used in a metric. · John Garry <hidden> · 2021-09-29
Re: [PATCH v9 00/13] Don't compute events that won't be used in a metric. · Ian Rogers <irogers@google.com> · 2021-09-29
Re: [PATCH v9 00/13] Don't compute events that won't be used in a metric. · Arnaldo Carvalho de Melo <acme@kernel.org> · 2021-09-29

From: Ian Rogers <irogers@google.com>
Date: 2021-09-29 16:11:00
Also in: lkml

On Wed, Sep 29, 2021 at 8:16 AM John Garry [off-list ref] wrote:

On 23/09/2021 08:46, Ian Rogers wrote:

quoted

For a metric like:
   EVENT1 if #smt_on else EVENT2

currently EVENT1 and EVENT2 will be measured and then when the metric
is reported EVENT1 or EVENT2 will be printed depending on the value
from smt_on() during the expr parsing. Computing both events is
unnecessary and can lead to multiplexing as discussed in this thread:
https://lore.kernel.org/lkml/20201110100346.2527031-1-irogers@google.com/ (local)

This change modifies expression parsing so that constants are
considered when building the set of ids (events) and only events not
contributing to a constant value are measured.

Based on some testing on my arm64 platform, no regression seen, so:

Tested-by: John Garry <redacted>

Awesome, much thanks Jiri, John, Andi for the reviews and testing!

Ian

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