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| author |   Chris Wilson <chris@chris-wilson.co.uk> | 2021-01-08 20:40:22 +0000 |
|---|---|---|
| committer | Chris Wilson <chris@chris-wilson.co.uk> | 2021-01-08 21:35:54 +0000 |
| commit | 0399d0e33a649a77c81a8bd2b2c5831608a489b6 (patch) | |
| tree | 68c48b6f07c3f7c7c873508ea3ca7e542aca9530 | |
| parent | drm/i915/selftests: Skip unstable timing measurements (diff) | |
| download | linux-dev-0399d0e33a649a77c81a8bd2b2c5831608a489b6.tar.xz linux-dev-0399d0e33a649a77c81a8bd2b2c5831608a489b6.zip | |
drm/i915/selftests: Rearrange ktime_get to reduce latency against CS
In our tests where we measure the elapsed time on both the CPU and CS
using a udelay, our CS results match the udelay much more accurately
than the ktime (even when using ktime_get_fast_ns). With preemption
disabled, we can go one step lower than ktime and use local_clock.
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2919
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210108204026.20682-3-chris@chris-wilson.co.uk
| -rw-r--r-- | drivers/gpu/drm/i915/gt/selftest_engine_pm.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/gpu/drm/i915/gt/selftest_engine_pm.c b/drivers/gpu/drm/i915/gt/selftest_engine_pm.c index ca080445695e..c3d965279fc3 100644 --- a/drivers/gpu/drm/i915/gt/selftest_engine_pm.c +++ b/drivers/gpu/drm/i915/gt/selftest_engine_pm.c @@ -112,11 +112,11 @@ static int __measure_timestamps(struct intel_context *ce, /* Run the request for a 100us, sampling timestamps before/after */ preempt_disable(); - *dt = ktime_get_raw_fast_ns(); + *dt = local_clock(); write_semaphore(&sema[2], 0); udelay(100); + *dt = local_clock() - *dt; write_semaphore(&sema[2], 1); - *dt = ktime_get_raw_fast_ns() - *dt; preempt_enable(); if (i915_request_wait(rq, 0, HZ / 2) < 0) { |