Re: [RFC][PATCH 3/3] account swapcache

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

On Mon, 14 Apr 2008 17:03:53 +0900
Daisuke Nishimura <d-nishimura@mtf.biglobe.ne.jp> wrote:

> I was thinking the case below.
> Assume some anonymous pages(mapped, referenced, !SwapCache)
> are being reclaimed.
> 

Numbering for below.

(1) > shrink_page_list()
(2)> 	-> add_to_swap() <- makes the page dirty.
(3)> 	->  try_to_unmap() <- uncharged from memcg and removed from mz->lru.
(4)> 	-> PageDirty() == true
(5)> 		sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced
(6)> 			goto keep_locked
(7)> 	-> unlocks the page and will work on other pages on page_list.
> 
> And, if on other CPU the process that owns those pages is exiting
> at the timing of my example above, those pages remain only on
> global lru, and are never charged(mapped) because the process exits.
> 
> I said "never" because once they are removed from mz->lru,
> mem_cgroup_isolate_pages() doesn't select those pages
> unless they are charged(mapped) again.
> 
I'm sorry if I don't catch your points.

Because of (1), it's marked as SwapCache.
At (2) , page is not removed from mz->lru because it's SwapCache. (see my patch)
page is still on mz->lru after (7).

After a process exits, this page will be reclaimed when page-recalim for
page_cgroup find this.

Thanks,
-Kame


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