@@ -4,7 +4,9 @@
*/
#define _GNU_SOURCE
#include <assert.h>
+#include <err.h>
#include <limits.h>
+#include <sched.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
@@ -76,8 +78,12 @@ unsigned long long calibrate(void)
bool approx(int i_one, int i_two)
{
- double one = i_one, one_bump = one * 0.01;
- double two = i_two, two_bump = two * 0.01;
+ /*
+ * This continues to be a noisy test. Instead of a 1% comparison
+ * go with 10%.
+ */
+ double one = i_one, one_bump = one * 0.1;
+ double two = i_two, two_bump = two * 0.1;
one_bump = one + MAX(one_bump, 2.0);
two_bump = two + MAX(two_bump, 2.0);
@@ -119,6 +125,32 @@ long compare(const char *name_one, const char *name_eval, const char *name_two,
return good ? 0 : 1;
}
+/* Pin to a single CPU so the benchmark won't bounce around the system. */
+void affinity(void)
+{
+ long cpu;
+ ulong ncores = sysconf(_SC_NPROCESSORS_CONF);
+ cpu_set_t *setp = CPU_ALLOC(ncores);
+ ulong setsz = CPU_ALLOC_SIZE(ncores);
+
+ /*
+ * Totally unscientific way to avoid CPUs that might be busier:
+ * choose the highest CPU instead of the lowest.
+ */
+ for (cpu = ncores - 1; cpu >= 0; cpu--) {
+ CPU_ZERO_S(setsz, setp);
+ CPU_SET_S(cpu, setsz, setp);
+ if (sched_setaffinity(getpid(), setsz, setp) == -1)
+ continue;
+ printf("Pinned to CPU %lu of %lu\n", cpu + 1, ncores);
+ goto out;
+ }
+ fprintf(stderr, "Could not set CPU affinity -- calibration may not work well");
+
+out:
+ CPU_FREE(setp);
+}
+
int main(int argc, char *argv[])
{
struct sock_filter bitmap_filter[] = {
@@ -153,6 +185,8 @@ int main(int argc, char *argv[])
system("grep -H . /proc/sys/net/core/bpf_jit_enable");
system("grep -H . /proc/sys/net/core/bpf_jit_harden");
+ affinity();
+
if (argc > 1)
samples = strtoull(argv[1], NULL, 0);
else
The seccomp benchmark test (for validating the benefit of bitmaps) can be sensitive to scheduling speed, so pin the process to a single CPU, which appears to significantly improve reliability, and loosen the "close enough" checking to allow up to 10% variance instead of 1%. Reported-by: kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202402061002.3a8722fd-oliver.sang@intel.com Cc: Mark Brown <broonie@kernel.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Will Drewry <wad@chromium.org> Signed-off-by: Kees Cook <keescook@chromium.org> --- v2: - improve comment about selecting CPU (broonie) - loosen variance check from 1% to 10% v1: https://lore.kernel.org/all/20240206095642.work.502-kees@kernel.org/ --- .../selftests/seccomp/seccomp_benchmark.c | 38 ++++++++++++++++++- 1 file changed, 36 insertions(+), 2 deletions(-)