[Intel-gfx] [PATCH igt] igt/perf_pmu: Bump batch_duration for legacy sampling inaccuracy

[Chris Wilson]

Since the legacy ringbuffer uses a sampling technique, it is limited to
an accuracy based on a 200Hz timer, or 5ms. We assert that measurements
are within 5%, so with a 100ms duration that gives us no room for the
systemmatic error in our sampling. Bump the duration to 500ms to give us
plenty of safety margin, if it then fails, it should not be due to the
sampling.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 tests/perf_pmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/perf_pmu.c b/tests/perf_pmu.c
index 61da224e..50ca7895 100644
--- a/tests/perf_pmu.c
+++ b/tests/perf_pmu.c
@@ -44,7 +44,7 @@
 IGT_TEST_DESCRIPTION("Test the i915 pmu perf interface");
 
 const double tolerance = 0.05f;
-const unsigned long batch_duration_ns = 100e6;
+const unsigned long batch_duration_ns = 500e6;
 
 static int open_pmu(uint64_t config)
 {
-- 
2.15.0