On Tue, Apr 5, 2022 at 5:12 AM Michal Koutný mkoutny@suse.com wrote:
On Fri, Apr 01, 2022 at 11:41:36AM -0700, "T.J. Mercier" tjmercier@google.com wrote:
This link doesn't work for me, but I think you're referring to the discussion about your "RAM_backed_buffers" comment from March 23rd.
(Oops, it's a non-public message. But yes, you guessed it right ;-))
Anyway the test I did goes like this: enable memcg and gpu cgoups tracking and run a process that allocates 100MiB of dmabufs. Observe memcg and gpu accounting values before and after the allocation.
Thanks for this measurement/dem/demoo.
Before # cat memory.current gpu.memory.current 14909440 system 0
<Test program does the allocation of 100MiB of dmabufs>
After # cat memory.current gpu.memory.current 48025600 system 104857600
So the memcg value increases by about 30 MiB while the gpu values increases by 100 MiB.
This is with kmem enabled, and the /proc/maps file for this process indicates that the majority of that 30 MiB is kernel memory.
I think this result shows that neither the kernel nor process memory overlap with the gpu cgroup tracking of these allocations.
It depends how the semantics of the 'system' entry is defined, no? As I grasped from other thread, the 'total' is going to be removed, so 'system' represents exclusively device memory?
That's right. The system charges (soon to be renamed "system-heap") result only from an allocator (in this case the system heap) deciding to call gpucg_try_charge for the buffer which is entirely device memory.
So despite the fact that these buffers are in main memory, they are allocated in a way that does not result in memcg attribution. (It looks to me like __GFP_ACCOUNT is not set for these.)
(I thought you knew what dmabufs your program used :-p)
I'm coming up to speed on a lot of new-to-me code here. :) Just for completeness, these buffers were allocated with libdmabufheap's AllocSystem.
So, the goal is to do the tracking and migrations only via the gpu cg layer, regardless how memcg charges it (or not).
(I have no opinion on that, I'm just summing it so that we're on the same page.)
Yes, this reflects my intention and current state of the code in this series.
Michal
Thanks, T.J.