Hi Johannes, On Mon, Sep 15, 2014 at 03:14:35PM -0400, Johannes Weiner wrote: > > Finally, my understanding (may be crazy!) how the things should be > > configured. Just like now, there should be mem_cgroup->res accounting > > and limiting total user memory (cache+anon) usage for processes inside > > cgroups. This is where there's nothing to do. However, mem_cgroup->memsw > > should be reworked to account *only* memory that may be swapped out plus > > memory that has been swapped out (i.e. swap usage). > > But anon pages are not a resource, they are a swap space liability. > Think of virtual memory vs. physical pages - the use of one does not > necessarily result in the use of the other. Without memory pressure, > anonymous pages do not consume swap space. > > What we *should* be accounting and limiting here is the actual finite > resource: swap space. Whenever we try to swap a page, its owner > should be charged for the swap space - or the swapout be rejected. I've been thinking quite a bit on the problem, and finally I believe you're right: a separate swap limit would be better than anon+swap. Provided we make the OOM-killer kill cgroups that exceed their soft limit and can't be reclaimed, it will solve the problem with soft limits I described above. Besides, comparing to anon+swap, swap limit would be more efficient (we only need to charge one res counter, not two) and understandable to users (it's simple to setup a limit for both kinds of resources then, because they never mix). Finally, we could transfer user configuration from cgroup v1 to v2 easily: just setup swap.limit to be equal to memsw.limit-mem.limit; it won't be exactly the same, but I bet nobody will notice any difference. So, at least for now, I vote for moving from mem+swap to swap accounting. Thanks, Vladimir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>