I think I know why it happens. At init all entity's rq gets assigned
to sched_list[0]. I put some prints to check what we compare in
drm_sched_entity_get_free_sched.
It turns out most of the time it compares zero values(num_jobs(0) <
min_jobs(0)) so most of the time 1st rq(sdma0, comp_1.0.0) was picked
by drm_sched_entity_get_free_sched.
Well that is expected because the unit tests always does
submission,wait,submission,wait,submission,wait.... So the number of
jobs in the scheduler becomes zero in between.
Even with multiple parallel instances of amdgpu_test, I haven't seen any
improvement in the load balance.
This patch was not correct , had an extra atomic_inc(num_jobs) in
drm_sched_job_init. This probably added bit of randomness I think,
which helped in better job distribution.
Mhm, that might not be a bad idea after all. We could rename num_jobs
into something like like score and do a +1 in
drm_sched_rq_add_entity() and a -1 in drm_sched_rq_remove_entity().
That should have pretty much the effect we want to have.
That's sounds good as well. I will create a patch.
I've updated my previous RFC patch which uses time consumed by each
sched for load balance with a twist of ignoring previously scheduled
sched/rq. Let me know what do you think.
I didn't had time yet to wrap my head around that in detail, but at
least of hand Luben is right that the locking looks really awkward.
I was unable to find a better way to do the locking part. My mail client
might've missed Luben's review, can't find it :/
Regards,
Nirmoy
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