On 14/05/2021 14:53, Christian König wrote:
David also said that you considered sysfs but were wary of exposing
process info in there. To clarify, my patch is not exposing sysfs
entry per process, but one per open drm fd.
Yes, we discussed this as well, but then rejected the approach.
To have useful information related to the open drm fd you need to
related that to process(es) which have that file descriptor open. Just
tracking who opened it first like DRM does is pretty useless on modern
systems.
We do update the pid/name for fds passed over unix sockets.
But an "lsof /dev/dri/renderD128" for example does exactly what top does
as well, it iterates over /proc and sees which process has that file open.
Lsof is quite inefficient for this use case. It has to open _all_ open
files for _all_ processes on the system to find a handful of ones which
may have the DRM device open.
So even with sysfs aid for discovery you are back to just going over all
files again.
For what use case?
To enable GPU usage in top we can do much better than iterate over all
open files in the system. We can start with a process if going with the
/proc proposal, or with the opened DRM file directly with the sysfs
proposal. Both are significantly fewer than total number of open files
across all processes.
Regards,
Tvrtko
