github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-05-25 15:41:52 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

drm/i915/selftests: Rearrange ktime_get to reduce latency against CS

Browse Source 
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
This commit is contained in:
Chris Wilson 2021-01-08 20:40:22 +00:00
parent c318a203ea
commit 0399d0e33a
1 changed files with 2 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/gpu/drm/i915/gt/selftest_engine_pm.c
View File

@ -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) {