From 010147f87a0c0e940fe8bf14abbd20c0224d58de Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Thu, 24 Sep 2026 16:27:57 -0300 Subject: [PATCH] perf mem record: Request PERF_SAMPLE_CPU by default The data type profiling per-sample stream keys cross-CPU contention on sample->cpu, which without PERF_SAMPLE_CPU is the "no CPU info" sentinel, making same-instance accesses from different cores indistinguishable from same-CPU traffic. 'perf mem record' already passes -d and -W to the record parser, add --sample-cpu and document it in perf-mem(1). Also grow rec_argv: the new entry overflows it on PMUs with separate load and store events, as the space for the fixed arguments was not reserved. Reviewed-by: Ian Rogers Reviewed-by: Namhyung Kim Assisted-by: LLM Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/Documentation/perf-mem.txt | 4 ++++ tools/perf/builtin-mem.c | 7 +++++-- 2 files changed, 9 insertions(+), 2 deletions(-) diff --git a/tools/perf/Documentation/perf-mem.txt b/tools/perf/Documentation/perf-mem.txt index 4d164836d094..fe51c5e3333d 100644 --- a/tools/perf/Documentation/perf-mem.txt +++ b/tools/perf/Documentation/perf-mem.txt @@ -14,6 +14,10 @@ DESCRIPTION ----------- "perf mem record" runs a command and gathers memory operation data from it, into perf.data. Perf record options are accepted and are passed through. +It also requests the address (-d), the weight (-W, where supported) and the +CPU id (--sample-cpu) of every sampled access by default; the CPU id is what +lets per-sample analysis tell reads and writes to the same data from +different cores apart from same-CPU traffic. "perf mem report" displays the result. It invokes perf report with the right set of options to display a memory access profile. By default, loads diff --git a/tools/perf/builtin-mem.c b/tools/perf/builtin-mem.c index 6101a26b3a78..ade53688ebcd 100644 --- a/tools/perf/builtin-mem.c +++ b/tools/perf/builtin-mem.c @@ -99,8 +99,8 @@ static int __cmd_record(int argc, const char **argv, struct perf_mem *mem, argc = parse_options(argc, argv, options, record_usage, PARSE_OPT_KEEP_UNKNOWN); - /* Max number of arguments multiplied by number of PMUs that can support them. */ - rec_argc = argc + 9 * (perf_pmu__mem_events_num_mem_pmus(pmu) + 1); + /* Max number of arguments per PMU plus the fixed ones added below. */ + rec_argc = argc + 8 + 9 * (perf_pmu__mem_events_num_mem_pmus(pmu) + 1); if (mem->cpu_list) rec_argc += 2; @@ -135,6 +135,9 @@ static int __cmd_record(int argc, const char **argv, struct perf_mem *mem, rec_argv[i++] = "-d"; + /* Cross-CPU contention keys on sample->cpu, -1 without PERF_SAMPLE_CPU. */ + rec_argv[i++] = "--sample-cpu"; + if (mem->phys_addr) rec_argv[i++] = "--phys-data";