Messages in this thread | | | Date | Tue, 28 Apr 2009 10:19:24 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH] fix leak of swap accounting as stale swap cache under memcg |
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On Tue, 28 Apr 2009 10:09:30 +0900 nishimura@mxp.nes.nec.co.jp wrote:
> > On Mon, 27 Apr 2009 21:08:56 +0900 > > Daisuke Nishimura <d-nishimura@mtf.biglobe.ne.jp> wrote: > > > >> > Index: mmotm-2.6.30-Apr24/mm/vmscan.c > >> > =================================================================== > >> > --- mmotm-2.6.30-Apr24.orig/mm/vmscan.c > >> > +++ mmotm-2.6.30-Apr24/mm/vmscan.c > >> > @@ -661,6 +661,9 @@ static unsigned long shrink_page_list(st > >> > if (PageAnon(page) && !PageSwapCache(page)) { > >> > if (!(sc->gfp_mask & __GFP_IO)) > >> > goto keep_locked; > >> > + /* avoid making more stale swap caches */ > >> > + if (memcg_stale_swap_congestion()) > >> > + goto keep_locked; > >> > if (!add_to_swap(page)) > >> > goto activate_locked; > >> > may_enter_fs = 1; > >> > > >> Well, as I mentioned before(http://marc.info/?l=linux-kernel&m=124066623510867&w=2), > >> this cannot avoid type-2(set !PageCgroupUsed by the owner process via > >> page_remove_rmap()->mem_cgroup_uncharge_page() before being added to swap cache). > >> If these swap caches go through shrink_page_list() without beeing freed > >> for some reason, these swap caches doesn't go back to memcg's LRU. > >> > >> Type-2 doesn't pressure memsw.usage, but you can see it by plotting > >> "grep SwapCached /proc/meminfo". > >> > >> And I don't think it's a good idea to add memcg_stale_swap_congestion() here. > >> This means less possibility to reclaim pages. > >> > > Hmm. maybe adding congestion_wait() ? > > > I don't think no hook before add_to_swap() is needed. > > >> Do you dislike the patch I attached in the above mail ? > >> > > I doubt whether the patch covers all type-2 case. > > > hmm, I didn't see any leak anymore when I tested the patch. >
At first, your patch == if (PageAnon(page) && !PageSwapCache(page)) { if (!(sc->gfp_mask & __GFP_IO)) goto keep_locked; - /* avoid making more stale swap caches */ - if (memcg_stale_swap_congestion()) - goto keep_locked; if (!add_to_swap(page)) goto activate_locked; + /* + * The owner process might have uncharged the page + * (by page_remove_rmap()) before it has been added + * to swap cache. + * Check it here to avoid making it stale. + */ + if (memcg_free_unused_swapcache(page)) + goto keep_locked; may_enter_fs = 1; } == Should be ==
if (PageAnon(page) && !PageSwapCache(page)) { ... // don't modify here } if (PageAnon(page) && PageSwapCache(page) && !page_mapped(page)) { if (try_to_free_page(page)) // or memcg_free_unused_swapcache() goto free_it; } == I think.
And we need hook to free_swap_and_cache() for handling PageWriteback() case.
> But because of machine time limit, I could only test for about 3 hours. > (I had seen some leak at that point before applying my patch) > I'll test for longer time if possible. > Sigh, my work time is also limited for these months ;(
> > I'll consider again and post v3. > > But I'll go into a series of holidays, so, may not come back until May/6. > > > It's the same for me :) > Enjoy good holidays :)
Thanks, -Kame
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