On 01/18/2019 12:10 PM, Koenig, Christian wrote: > Am 18.01.19 um 16:21 schrieb Grodzovsky, Andrey: >> On 01/18/2019 04:25 AM, Koenig, Christian wrote: >>> [SNIP] >>>>>>> Re-arming the timeout should probably have a much reduced value >>>>>>> when the job hasn't changed. E.g. something like a few ms. >>>> Now i got thinking about non hanged job in progress (job A) and let's >>>> say it's a long job , it just started executing but due to time out of >>>> another job (job B) on another (or this scheduler) it's parent cb got >>>> disconnected, we disarmed the tdr timer for the job's scheduler, >>>> meanwhile the timed out job did manage to complete before HW reset >>>> check and hence we skip HW reset, attach back the cb and rearm job's A >>>> tdr timer with a future value of few ms only - aren't we going to get >>>> false tdr triggered on job B now because we didn't let it enough time >>>> to run and complete ? I would prefer the other extreme of longer time >>>> for time out to trigger then false TDR. Optimally we would have per >>>> job timer and rearm to exactly the reminder of it's time out value - >>>> but we gave up on per job tdr work long ago. >>> Well we only re-arm the timeout with a shorter period if it already >>> triggered once. If we just suspend the timeout then we should still use >>> the longer period. >> Can you explain more on this ? I don't get it. > See drm_sched_job_timedout(), we re-arm the timeout at the end of the > procedure. > > We should change that and re-arm the timer with a much lower timeout if > the job is still not finished. > > Christian. I still don't see how this can fix the problem of of long job in progress triggering false tdr if no HW reset was done, but maybe I am missing other pieces you have in mind, I will finish the patch and send it and then we can be more specific based on the code. Andrey > >> Andrey >> >>>> In general the more i think about it (correct me if I am wrong) I am >>>> less sure how much the optimization feature is useful - if job's time >>>> out did trigger what are the chances that the little more time we give >>>> it between beginning of tdr function and the time we do start the >>>> actual HW reset will be exactly what it needed to complete. Also, this >>>> is still not water proof as the job might complete and signal it's HW >>>> fence exactly after we checked for completion but before starting the >>>> HW reset code. >>> I don't see this as an optimization, but rather as mandatory for correct >>> operation. >>> >>> See without this we can run into issues because we execute jobs multiple >>> times. That can still happen with this clean handling, but it is much >>> more unlikely. >>> >>> Christian. >>> >>>> Andrey >>>> >>>>>> By unchanged you mean when we didn't resubmit the job because of the >>>>>> optimized non HW reset, right ? >>>>> Correct, yes. >>>>> >>>>>>>> About flushing tdr jobs in progress from .free_job cb - looks like >>>>>>>> drm_sched_job_finish->cancel_delayed_work_sync is not enough, we >>>>>>>> still need to take care of flushing all sced->work_tdr for a >>>>>>>> device and for all devices in hive for XGMI. >>>>>>>> What do you think ? >>>>>>> Why should that be necessary? We only wait for the delayed work to >>>>>>> make sure that the job is not destroyed while dealing with it. >>>>>>> >>>>>>> Christian. >>>>>> But we might not be waiting for the correct sched->work_tdr, we do >>>>>> the reset routine for all schedulers in a device accessing their >>>>>> jobs too and not only for the scheduler to which the job belongs. >>>>>> For XGMI not only that, we reset all the devices in the hive. >>>>> That is harmless you only need to wait for the work_tdr of the >>>>> current scheduler, not for all of them. >>>>> >>>>>> I was thinking, amdgpu driver is not even interested in allowing >>>>>> multiple sced->tdr to execute together - we have to serialize all of >>>>>> them anyway with the trylock mutex (even without XGMI), v3d in >>>>>> v3d_job_timedout seems also to reset all of his schedulers from the >>>>>> tdr work. Would it make sense to provide the sched->work_td as init >>>>>> parameter to scheduler (same one for all schedulers) so we can >>>>>> enforce serialization by disallowing more then 1 tdr work to execute >>>>>> in the same time ? Other drivers interested to do in parallel can >>>>>> provide unique sched->work_tdr per scheduler. This does imply >>>>>> drm_sched_job_timedout has to removed and delegated to specific >>>>>> driver implementation as probably other code dealing with >>>>>> sched->work_tdr... Maybe even move tdr handling to the driver all >>>>>> together ? >>>>> Yeah, I was thinking something similar. The problem with this >>>>> approach is that a delayed work item can have only one delay, but for >>>>> multiple engines we need multiple delays. >>>>> >>>>> What we could do is to make it a timer instead and raise the work >>>>> item from the device specific callback. >>>>> >>>>> But that doesn't really saves us the stop all schedulers trouble, so >>>>> it doesn't buy us much in the end if I see this correctly. >>>>> >>>>> Christian. >>> _______________________________________________ >>> amd-gfx mailing list >>> amd-gfx@xxxxxxxxxxxxxxxxxxxxx >>> https://lists.freedesktop.org/mailman/listinfo/amd-gfx _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
