Re: [PATCH i-g-t 2/3] lib: Align ring measurement to timer

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On 30/05/18 03:33, Chris Wilson wrote:
After hitting the SIGINT from execbuf, wait until the next timer signal
before trying again. This aligns the start of the ioctl to the timer,
hopefully maximising the amount of time we have for processing before
the next signal -- trying to prevent the case where we are scheduled out
in the middle of processing and so hit the timer signal too early.

References: https://bugs.freedesktop.org/show_bug.cgi?id=106695
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>

Not sure I understand what is the sequence of events, is the problem we get a signal in the middle of a 'good' execbuf and exit the while loop prematurely? If so maybe we can also think of making the timer 'VIRTUAL' so that it would decrement only when the process is executing.

Thanks,
Antonio

---
  lib/i915/gem_ring.c | 2 ++
  1 file changed, 2 insertions(+)

diff --git a/lib/i915/gem_ring.c b/lib/i915/gem_ring.c
index 7d64165eb..0c061000c 100644
--- a/lib/i915/gem_ring.c
+++ b/lib/i915/gem_ring.c
@@ -96,6 +96,8 @@ __gem_measure_ring_inflight(int fd, unsigned int engine, enum measure_ring_flags
  		if (last == count)
  			break;
+ /* sleep until the next timer interrupt (woken on signal) */
+		pause();

Does it cause any (sensible) slowdown?

Thanks,
Antonio

  		last = count;
  	} while (1);
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