Hi, On 19/07/2023 21:31, T.J. Mercier wrote:
On Wed, Jul 12, 2023 at 4:47 AM Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx> wrote:drm.memory.stat A nested file containing cumulative memory statistics for the whole sub-hierarchy, broken down into separate GPUs and separate memory regions supported by the latter. For example:: $ cat drm.memory.stat card0 region=system total=12898304 shared=0 active=0 resident=12111872 purgeable=167936 card0 region=stolen-system total=0 shared=0 active=0 resident=0 purgeable=0 Card designation corresponds to the DRM device names and multiple line entries can be present per card. Memory region names should be expected to be driver specific with the exception of 'system' which is standardised and applicable for GPUs which can operate on system memory buffers. Sub-keys 'resident' and 'purgeable' are optional. Per category region usage is reported in bytes. * Feedback from people interested in drm.active_us and drm.memory.stat is required to understand the use cases and their usefulness (of the fields). Memory stats are something which was easy to add to my series, since I was already working on the fdinfo memory stats patches, but the question is how useful it is.Hi Tvrtko, I think this style of driver-defined categories for reporting of memory could potentially allow us to eliminate the GPU memory tracking tracepoint used on Android (gpu_mem_total). This would involve reading drm.memory.stat at the root cgroup (I see it's currently disabled on
I can put it available under root too, don't think there is any technical reason to not have it. In fact, now that I look at it again, memory.stat is present on root so that would align with my general guideline to keep the two as similar as possible.
the root), which means traversing the whole cgroup tree under the cgroup lock to generate the values on-demand. This would be done rarely, but I still wonder what the cost of that would turn out to be.
Yeah that's ugly. I could eliminate cgroup_lock by being a bit smarter. Just didn't think it worth it for the RFC.
Basically to account memory stats for any sub-tree I need the equivalent one struct drm_memory_stats per DRM device present in the hierarchy. So I could pre-allocate a few and restart if run out of spares, or something. They are really small so pre-allocating a good number, based on past state or something, should would good enough. Or even total number of DRM devices in a system as a pessimistic and safe option for most reasonable deployments.
The drm_memory_stats categories in the output don't seem like a big value-add for this use-case, but no real objection to them being
You mean the fact there are different categories is not a value add for your use case because you would only use one?
The idea was to align 1:1 with DRM memory stats fdinfo and somewhat emulate how memory.stat also offers a breakdown.
there. I know it's called the DRM cgroup controller, but it'd be nice if there were a way to make the mem tracking part work for any driver that wishes to participate as many of our devices don't use a DRM driver. But making that work doesn't look like it would fit very
Ah that would be a challenge indeed to which I don't have any answers right now.
Hm if you have a DRM device somewhere in the chain memory stats would still show up. Like if you had a dma-buf producer which is not a DRM driver, but then that buffer was imported by a DRM driver, it would show up in a cgroup. Or vice-versa. But if there aren't any in the whole chain then it would not.
cleanly into this controller, so I'll just shut up now.
Not all all, good feedback! Regards, Tvrtko
