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Date: Wed, 12 Aug 2020 17:33:54 +0200 From: Christian König <ckoenig.leichtzumerken@...il.com> To: Steven Rostedt <rostedt@...dmis.org> Cc: christian.koenig@....com, amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, Shashank.Sharma@....com, daniel.vetter@...ll.ch, alexander.deucher@....com Subject: Re: [PATCH] drm/amdgpu: adjust the pid in the grab_id trace point Am 12.08.20 um 17:19 schrieb Steven Rostedt: > On Wed, 12 Aug 2020 16:36:36 +0200 > Christian König <ckoenig.leichtzumerken@...il.com> wrote: > >> Am 12.08.20 um 16:17 schrieb Steven Rostedt: >>> On Fri, Aug 07, 2020 at 03:36:58PM +0200, Christian König wrote: >>>> Trace something useful instead of the pid of a kernel thread here. >>>> >>>> Signed-off-by: Christian König <christian.koenig@....com> >>>> --- >>>> drivers/gpu/drm/amd/amdgpu/amdgpu_trace.h | 1 + >>>> 1 file changed, 1 insertion(+) >>>> >>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_trace.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_trace.h >>>> index 5da20fc166d9..07f99ef69d91 100644 >>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_trace.h >>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_trace.h >>>> @@ -228,6 +228,7 @@ TRACE_EVENT(amdgpu_vm_grab_id, >>>> ), >>>> >>>> TP_fast_assign( >>>> + __entry->ent.pid = vm->task_info.pid; >>> If the ent.pid is not the pid you are interested in for this trace event, just >>> add a "pid" field to the trace event and place it there. Do not modify the >>> generic pid that is recorded, as we would like that to be consistent for all >>> trace events. >> The problem my userspace guys have is that this doesn't work with >> "trace-cmd -P $pid". >> >> But I think I can teach them how filters work :) > Yep, trace-cmd record -e event -f "pid == $pid" > >>> The "ent.pid" turns into "common_pid" in the field, leaving "pid" free to use. >>> Other trace events (like sched_waking) record a pid field that is not the same >>> as the pid of the executing task. >> Yes, we thought about this alternative as well. >> >>> The "ent.pid" should always be the pid of the task that executed the event. >> Why? For the case here we just execute a work item in the background for >> an userspace process. >> >> Tracing the pid of the worker pool which executes it doesn't seem to >> make to much sense. > Maybe not for you, but it does for me. All trace events show what > happened when it happened and who executed it. I like to see what > worker threads are executing. I may filter on the worker thread, and by > changing the ent.pid, I wont see what it is doing. That's enough explanation for me. Going with the separate pid field then. Thanks, Christian. > > That said, I think I may add a feature to a trace evnt for a special filter > to say, "test field to the set_event_pid", and if it exists in that > file to include that event in the filtered trace. This would include > sched_waking trace events as well. > > That way "trace-cmd record -P $pid" will still work for your case. > > -- Steve
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