github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-07-27 17:47:41 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

selftests/bpf: Filter timing outliers with IQR in batch-timing library

Browse Source 
System noise (timer interrupts, scheduling) can inflate the reported
stddev.  tcp-v4-syn showed stddev 37.86 ns without filtering vs
0.16 ns with filtering on the same run data.

Filter samples outside [Q1 - 1.5*IQR, Q3 + 1.5*IQR] before computing
statistics.  Scenarios with genuinely wide distributions have large IQR
so the fences stay wide and the filter has minimal effect.

Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Link: https://lore.kernel.org/r/20260520133338.3392667-4-puranjay@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Puranjay Mohan 2026-05-20 06:33:32 -07:00 committed by Alexei Starovoitov
parent 12e896b979
commit abac8acb63
1 changed files with 26 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
tools/testing/selftests/bpf/benchs/bench_bpf_timing.c
View File

@ -65,6 +65,31 @@ static int collect_samples(struct bpf_bench_timing *t,
return total;
}
static int filter_outliers_iqr(double *sorted, int n)
{
double q1, q3, iqr, lo, hi;
int start = 0, end = n;
if (n < 8)
return n;
q1 = sorted[n / 4];
q3 = sorted[3 * n / 4];
iqr = q3 - q1;
lo = q1 - 1.5 * iqr;
hi = q3 + 1.5 * iqr;
while (start < end && sorted[start] < lo)
start++;
while (end > start && sorted[end - 1] > hi)
end--;
if (start > 0)
memmove(sorted, sorted + start, (end - start) * sizeof(double));
return end - start;
}
static void compute_stats(const double *sorted, int n,
struct timing_stats *s)
{
@ -150,6 +175,7 @@ void bpf_bench_timing_report(struct bpf_bench_timing *t, const char *name, const
return;
}
total = filter_outliers_iqr(all, total);
compute_stats(all, total, &s);
if (t->machine_readable) {