On 11/2/2018 7:07 PM, Koenig, Christian wrote:
Am 02.11.18 um 14:25 schrieb Sharat Masetty:
On 11/2/2018 4:09 PM, Koenig, Christian wrote:
Am 02.11.18 um 11:31 schrieb Sharat Masetty:
Add an optional backend function op which will let the scheduler
clients
know when the timeout got scheduled on the scheduler instance. This
will
help drivers with multiple schedulers(one per ring) measure time
spent on
the ring accurately, eventually helping with better timeout detection.
Signed-off-by: Sharat Masetty <smasetty@xxxxxxxxxxxxxx>
Well, NAK. drm_sched_start_timeout() is called whenever the timer needs
to run, but that doesn't mean that the timer is started (e.g. it can
already be running).
So the callback would be called multiple times and not reflect the
actual job run time.
Additional to that it can be racy, e.g. we can complete multiple jobs at
a time before the timer is started again.
If you want to accurately count how much time you spend on each job/ring
you need to do this by measuring the time inside your driver instead.
E.g. for amdgpu I would get the time first in amdgpu_job_run() and then
again in amdgpu_job_free_cb() and calculate the difference.
Hi Christian,
Thank you for the comments and apologies if this was confusing. All I
want to determine(more accurately) is that when the scheduler instance
timer of say 500 ms goes off, is if the ring(associated with the
scheduler instance) actually spent 500 ms on the hardware - and for
this I need to know in the driver space when the timer actually started.
In msm hardware we have ring preemption support enabled and the kernel
driver triggers a preemption switch to a higher priority ring if there
is work available on that ring for the GPU to work on. So in the
presence of preemption it is possible that a lower priority ring did
not actually get to spend the full 500 ms and this is what I am trying
to catch with this callback.
I am *not* trying to profile per job time consumption with this.
Well, NAK. drm_sched_start_timeout() is called whenever the timer needs
to run, but that doesn't mean that the timer is started (e.g. it can
already be running).
Regarding the case where the timer may already be running - good
point, but it should be easy to address the scenario. I will check the
output
of schedule_delayed_work() and only call the callback(new proposed) if
the timer was really scheduled.
Yeah, that should work.
In summary, when this timedout_job() callback is called, it is assumed
that the job actually did time out from the POV of the scheduler, but
this will not hold true with preemption switching and that is what I
am trying to better address with this patch.
Mhm, so what you actually need is to suspend the timeout when the lower
priority ring is preempted and resume it when it is started again? I
wonder if that wouldn't be simpler.
We have support for ring preemption as well, but not implemented yet. So
it would be nice to have something that works for everybody.
But on the other hand a callback to notify the driver that the timer
started isn't so bad either.
Hi Christian,
Yes something like a suspend timeout would be simpler for the drivers,
but I could not find anything which does this for the delayed work or
even for the general timers. All I could find was cancel/delete.
In lieu of this, I chose this approach. If you like it this way(proposed
patch), then I will address the review comments and re-spin... please
let me know.
Sharat
Regards,
Christian.
Sharat
Regards,
Christian.
---
Here is an example of how I plan to use this new function callback.
[1] https://patchwork.freedesktop.org/patch/254227/
drivers/gpu/drm/scheduler/sched_main.c | 7 ++++++-
include/drm/gpu_scheduler.h | 6 ++++++
2 files changed, 12 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/scheduler/sched_main.c
b/drivers/gpu/drm/scheduler/sched_main.c
index c993d10..afd461e 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -192,8 +192,13 @@ bool drm_sched_dependency_optimized(struct
dma_fence* fence,
static void drm_sched_start_timeout(struct drm_gpu_scheduler *sched)
{
if (sched->timeout != MAX_SCHEDULE_TIMEOUT &&
- !list_empty(&sched->ring_mirror_list))
+ !list_empty(&sched->ring_mirror_list)) {
+
schedule_delayed_work(&sched->work_tdr, sched->timeout);
+
+ if (sched->ops->start_timeout_notify)
+ sched->ops->start_timeout_notify(sched);
+ }
}
/* job_finish is called after hw fence signaled
diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
index d87b268..faf28b4 100644
--- a/include/drm/gpu_scheduler.h
+++ b/include/drm/gpu_scheduler.h
@@ -239,6 +239,12 @@ struct drm_sched_backend_ops {
* and it's time to clean it up.
*/
void (*free_job)(struct drm_sched_job *sched_job);
+
+ /*
+ * (Optional) Called to let the driver know that a timeout
detection
+ * timer has been started.
+ */
+ void (*start_timeout_notify)(struct drm_gpu_scheduler *sched);
};
/**
--
1.9.1
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