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perf pmu: Don't de-duplicate core PMUs

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Arm PMUs have a suffix, either a single decimal (armv8_pmuv3_0) or 3 hex
digits which (armv8_cortex_a53) which Perf assumes are both strippable
suffixes for the purposes of deduplication. S390 "cpum_cf" is a
similarly suffixed core PMU but is only two characters so is not treated
as strippable because the rules are a minimum of 3 hex characters or 1
decimal character.

There are two paths involved in listing PMU events:

 * HW/cache event printing assumes core PMUs don't have suffixes so
   doesn't try to strip.
 * Sysfs PMU events share the printing function with uncore PMUs which
   strips.

This results in slightly inconsistent Perf list behavior if a core PMU
has a suffix:

  # perf list
  ...
  armv8_pmuv3_0/branch-load-misses/
  armv8_pmuv3/l3d_cache_wb/          [Kernel PMU event]
  ...

Fix it by partially reverting back to the old list behavior where
stripping was only done for uncore PMUs. For example commit 8d9f5146f5da
("perf pmus: Sort pmus by name then suffix") mentions that only PMUs
starting 'uncore_' are considered to have a potential suffix. This
change doesn't go back that far, but does only strip PMUs that are
!is_core. This keeps the desirable behavior where the many possibly
duplicated uncore PMUs aren't repeated, but it doesn't break listing for
core PMUs.

Searching for a PMU continues to use the new stripped comparison
functions, meaning that it's still possible to request an event by
specifying the common part of a PMU name, or even open events on
multiple similarly named PMUs. For example:

  # perf stat -e armv8_cortex/inst_retired/

  5777173628      armv8_cortex_a53/inst_retired/          (99.93%)
  7469626951      armv8_cortex_a57/inst_retired/          (49.88%)

Fixes: 3241d46f5f54 ("perf pmus: Sort/merge/aggregate PMUs like mrvl_ddr_pmu")
Suggested-by: Ian Rogers <irogers@google.com>
Signed-off-by: James Clark <james.clark@arm.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Cc: robin.murphy@arm.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240626145448.896746-3-james.clark@arm.com
This commit is contained in:
James Clark 2024-06-26 15:54:46 +01:00 committed by Namhyung Kim
parent 3e0bf9fde2
commit 7afbf90ea2
1 changed files with 21 additions and 6 deletions
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27
tools/perf/util/pmu.c
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@ -847,6 +847,23 @@ __weak const struct pmu_metrics_table *pmu_metrics_table__find(void)
return perf_pmu__find_metrics_table(NULL);
}
/**
* Return the length of the PMU name not including the suffix for uncore PMUs.
*
* We want to deduplicate many similar uncore PMUs by stripping their suffixes,
* but there are never going to be too many core PMUs and the suffixes might be
* interesting. "arm_cortex_a53" vs "arm_cortex_a57" or "cpum_cf" for example.
*
* @skip_duplicate_pmus: False in verbose mode so all uncore PMUs are visible
*/
static size_t pmu_deduped_name_len(const struct perf_pmu *pmu, const char *name,
bool skip_duplicate_pmus)
{
return skip_duplicate_pmus && !pmu->is_core
? pmu_name_len_no_suffix(name)
: strlen(name);
}
/**
* perf_pmu__match_ignoring_suffix - Does the pmu_name match tok ignoring any
* trailing suffix? The Suffix must be in form
@ -1796,9 +1813,8 @@ static char *format_alias(char *buf, int len, const struct perf_pmu *pmu,
const struct perf_pmu_alias *alias, bool skip_duplicate_pmus)
{
struct parse_events_term *term;
size_t pmu_name_len = skip_duplicate_pmus
? pmu_name_len_no_suffix(pmu->name)
: strlen(pmu->name);
size_t pmu_name_len = pmu_deduped_name_len(pmu, pmu->name,
skip_duplicate_pmus);
int used = snprintf(buf, len, "%.*s/%s", (int)pmu_name_len, pmu->name, alias->name);
list_for_each_entry(term, &alias->terms.terms, list) {
@ -1839,9 +1855,8 @@ int perf_pmu__for_each_event(struct perf_pmu *pmu, bool skip_duplicate_pmus,
size_t buf_used, pmu_name_len;
info.pmu_name = event->pmu_name ?: pmu->name;
pmu_name_len = skip_duplicate_pmus
? pmu_name_len_no_suffix(info.pmu_name)
: strlen(info.pmu_name);
pmu_name_len = pmu_deduped_name_len(pmu, info.pmu_name,
skip_duplicate_pmus);
info.alias = NULL;
if (event->desc) {
info.name = event->name;