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perf stat: Read tool events last

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When reading a metric like memory bandwidth on multiple sockets, the
additional sockets will be on CPUS > 0. Because of the affinity
reading, the counters are read on CPU 0 along with the time, then the
later sockets are read. This can lead to the later sockets having a
bandwidth larger than is possible for the period of time. To avoid
this move the reading of tool events to occur after all other events
are read.

Signed-off-by: Ian Rogers <irogers@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
This commit is contained in:
Ian Rogers 2025-11-18 13:13:24 -08:00 committed by Namhyung Kim
parent 87cc0b44fc
commit 51d87d977e
1 changed files with 39 additions and 6 deletions
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45
tools/perf/builtin-stat.c
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@ -366,7 +366,7 @@ static int read_counter_cpu(struct evsel *counter, int cpu_map_idx)
return 0;
}
static int read_affinity_counters(void)
static int read_counters_with_affinity(void)
{
struct evlist_cpu_iterator evlist_cpu_itr;
struct affinity saved_affinity, *affinity;
@ -387,6 +387,9 @@ static int read_affinity_counters(void)
if (evsel__is_bpf(counter))
continue;
if (evsel__is_tool(counter))
continue;
if (!counter->err)
counter->err = read_counter_cpu(counter, evlist_cpu_itr.cpu_map_idx);
}
@ -412,16 +415,46 @@ static int read_bpf_map_counters(void)
return 0;
}
static int read_counters(void)
static int read_tool_counters(void)
{
if (!stat_config.stop_read_counter) {
if (read_bpf_map_counters() ||
read_affinity_counters())
return -1;
struct evsel *counter;
evlist__for_each_entry(evsel_list, counter) {
int idx;
if (!evsel__is_tool(counter))
continue;
perf_cpu_map__for_each_idx(idx, counter->core.cpus) {
if (!counter->err)
counter->err = read_counter_cpu(counter, idx);
}
}
return 0;
}
static int read_counters(void)
{
int ret;
if (stat_config.stop_read_counter)
return 0;
// Read all BPF counters first.
ret = read_bpf_map_counters();
if (ret)
return ret;
// Read non-BPF and non-tool counters next.
ret = read_counters_with_affinity();
if (ret)
return ret;
// Read the tool counters last. This way the duration_time counter
// should always be greater than any other counter's enabled time.
return read_tool_counters();
}
static void process_counters(void)
{
struct evsel *counter;