On Wed, Oct 28, 2020 at 10:56:20AM +0800, Muchun Song wrote: > On Wed, Oct 28, 2020 at 2:48 AM Roman Gushchin <[email protected]> wrote: > > > > On Tue, Oct 27, 2020 at 04:02:55PM +0800, Muchun Song wrote: > > > If we reparent the slab objects to the root memcg, when we free > > > the slab object, we need to update the per-memcg vmstats to keep > > > it correct for the root memcg. Now this at least affects the vmstat > > > of NR_KERNEL_STACK_KB for !CONFIG_VMAP_STACK when the thread stack > > > size is smaller than the PAGE_SIZE. > > > > > > Fixes: ec9f02384f60 ("mm: workingset: fix vmstat counters for shadow > > > nodes") > > > Signed-off-by: Muchun Song <[email protected]> > > > > Can you, please, drop this patch for now? > > > > I'm working on a bigger cleanup related to the handling of the root memory > > cgroup (I sent a link earlier in this thread), which already does a similar > > change. > > There are several issues like this one, so it will be nice to fix them all > > at once. > > I have read the patch of https://lkml.org/lkml/2020/10/14/869. You > mean this patch > fixes this issue? It chooses to uncharge the root memcg. But here we may need > to > uncharge the root memcg to keep root vmstats correct. If we do not do > this, we can > see the wrong vmstats via root memory.stat(e.g. NR_KERNEL_STACK_KB).
I pointed at a different patch in the same thread (it looks like you read the first one): https://lkml.org/lkml/2020/10/21/612 It contained the following part: @@ -868,7 +860,7 @@ void __mod_lruvec_slab_state(void *p, enum node_stat_item idx, int val) memcg = mem_cgroup_from_obj(p); /* Untracked pages have no memcg, no lruvec. Update only the node */ - if (!memcg || memcg == root_mem_cgroup) { + if (!memcg) { __mod_node_page_state(pgdat, idx, val); } else { lruvec = mem_cgroup_lruvec(memcg, pgdat); So it's exactly what your patch does. Thanks!
