Re: [PATCH 1/4] memcg: fix split_huge_page_refcounts

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Wed, 28 Dec 2011 16:20:25 -0800 (PST)
Hugh Dickins <hughd@google.com> wrote:

> This patch started off as a cleanup: __split_huge_page_refcounts() has to
> cope with two scenarios, when the hugepage being split is already on LRU,
> and when it is not; but why does it have to split that accounting across
> three different sites?  Consolidate it in lru_add_page_tail(), handling
> evictable and unevictable alike, and use standard add_page_to_lru_list()
> when accounting is needed (when the head is not yet on LRU).
> 
> But a recent regression in -next, I guess the removal of PageCgroupAcctLRU
> test from mem_cgroup_split_huge_fixup(), makes this now a necessary fix:
> under load, the MEM_CGROUP_ZSTAT count was wrapping to a huge number,
> messing up reclaim calculations and causing a freeze at rmdir of cgroup.
> 
> Add a VM_BUG_ON to mem_cgroup_lru_del_list() when we're about to wrap
> that count - this has not been the only such incident.  Document that
> lru_add_page_tail() is for Transparent HugePages by #ifdef around it.
> 
> Signed-off-by: Hugh Dickins <hughd@google.com>

seems saner.
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Thank you.

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