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perf sample: Make user_regs and intr_regs optional

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The struct dump_regs contains 512 bytes of cache_regs, meaning the two
values in perf_sample contribute 1088 bytes of its total 1384 bytes
size. Initializing this much memory has a cost reported by Tavian
Barnes <tavianator@tavianator.com> as about 2.5% when running `perf
script --itrace=i0`:
https://lore.kernel.org/lkml/d841b97b3ad2ca8bcab07e4293375fb7c32dfce7.1736618095.git.tavianator@tavianator.com/

Adrian Hunter <adrian.hunter@intel.com> replied that the zero
initialization was necessary and couldn't simply be removed.

This patch aims to strike a middle ground of still zeroing the
perf_sample, but removing 79% of its size by make user_regs and
intr_regs optional pointers to zalloc-ed memory. To support the
allocation accessors are created for user_regs and intr_regs. To
support correct cleanup perf_sample__init and perf_sample__exit
functions are created and added throughout the code base.

Signed-off-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250113194345.1537821-1-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
This commit is contained in:
Ian Rogers
2025-01-13 11:43:45 -08:00
committed by Namhyung Kim
parent 08d9e88348
commit dc6d2bc2d8
34 changed files with 448 additions and 191 deletions
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10
tools/perf/builtin-script.c
View File

@@ -783,14 +783,20 @@ tod_scnprintf(struct perf_script *script, char *buf, int buflen,
static int perf_sample__fprintf_iregs(struct perf_sample *sample,
struct perf_event_attr *attr, const char *arch, FILE *fp)
{
return perf_sample__fprintf_regs(&sample->intr_regs,
if (!sample->intr_regs)
return 0;
return perf_sample__fprintf_regs(perf_sample__intr_regs(sample),
attr->sample_regs_intr, arch, fp);
}
static int perf_sample__fprintf_uregs(struct perf_sample *sample,
struct perf_event_attr *attr, const char *arch, FILE *fp)
{
return perf_sample__fprintf_regs(&sample->user_regs,
if (!sample->user_regs)
return 0;
return perf_sample__fprintf_regs(perf_sample__user_regs(sample),
attr->sample_regs_user, arch, fp);
}