On Thu, May 23, 2019 at 01:43:49PM -0400, Johannes Weiner wrote: > I noticed that recent upstream kernels don't account the xarray nodes > of the page cache to the allocating cgroup, like we used to do for the > radix tree nodes. > > This results in broken isolation for cgrouped apps, allowing them to > escape their containment and harm other cgroups and the system with an > excessive build-up of nonresident information. > > It also breaks thrashing/refault detection because the page cache > lives in a different domain than the xarray nodes, and so the shadow > shrinker can reclaim nonresident information way too early when there > isn't much cache in the root cgroup. > > I'm not quite sure how to fix this, since the xarray code doesn't seem > to have per-tree gfp flags anymore like the radix tree did. We cannot > add SLAB_ACCOUNT to the radix_tree_node_cachep slab cache. And the > xarray api doesn't seem to really support gfp flags, either (xas_nomem > does, but the optimistic internal allocations have fixed gfp flags). Would it be a problem to always add __GFP_ACCOUNT to the fixed flags? I don't really understand cgroups.
