On Mon 23-01-23 19:17:23, T.J. Mercier wrote:
When a buffer is exported to userspace, use memcg to attribute the buffer to the allocating cgroup until all buffer references are released.
Is there any reason why this memory cannot be charged during the allocation (__GFP_ACCOUNT used)? Also you do charge and account the memory but underlying pages do not know about their memcg (this is normally done with commit_charge for user mapped pages). This would become a problem if the memory is migrated for example. This also means that you have to maintain memcg reference outside of the memcg proper which is not really nice either. This mimicks tcp kmem limit implementation which I really have to say I am not a great fan of and this pattern shouldn't be coppied.
Also you are not really saying anything about the oom behavior. With this implementation the kernel will try to reclaim the memory and even trigger the memcg oom killer if the request size is <= 8 pages. Is this a desirable behavior?