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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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9
tools/perf/util/sample.h
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@@ -114,14 +114,19 @@ struct perf_sample {
struct ip_callchain *callchain;
struct branch_stack *branch_stack;
u64 *branch_stack_cntr;
struct regs_dump user_regs;
struct regs_dump intr_regs;
struct regs_dump *user_regs;
struct regs_dump *intr_regs;
struct stack_dump user_stack;
struct sample_read read;
struct aux_sample aux_sample;
struct simd_flags simd_flags;
};
void perf_sample__init(struct perf_sample *sample, bool all);
void perf_sample__exit(struct perf_sample *sample);
struct regs_dump *perf_sample__user_regs(struct perf_sample *sample);
struct regs_dump *perf_sample__intr_regs(struct perf_sample *sample);
/*
* raw_data is always 4 bytes from an 8-byte boundary, so subtract 4 to get
* 8-byte alignment.