On Tue, 8 Mar 2011 11:04:43 +0900 Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx> wrote: > On Tue, 8 Mar 2011 10:02:42 +0900 > KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > > > On Tue, 8 Mar 2011 09:59:39 +0900 > > Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx> wrote: > > > > > On Mon, 7 Mar 2011 15:00:49 +0900 > > > KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > > > > > > > At this point, I'm not sure this is a fix for > > > > https://bugzilla.kernel.org/show_bug.cgi?id=30432. > > > > > > > > The behavior seems very similar to SwapCache case and this is a possible > > > > bug and this patch can be a fix. Nishimura-san, how do you think ? > > > > > > > As long as I can read the source code, I also think this is a possible bug. > > > > > > > But I'm not sure how to test this....please review. > > > > > > > > = > > > > fs/fuse/dev.c::fuse_try_move_page() does > > > > > > > > (1) remove a page from page cache by ->steal() > > > > (2) re-add the page to page cache > > > > (3) link the page to LRU if it was _not_ on LRU at (1) > > > > > > > > > > > > This implies the page can be _on_ LRU when add_to_page_cache_locked() is called. > > > > So, the page is added to a memory cgroup while it's on LRU. > > > > > > > > This is the same behavior as SwapCache, 'newly charged pages may be on LRU' > > > > and needs special care as > > > > - remove page from old memcg's LRU before overwrite pc->mem_cgroup. > > > > - add page to new memcg's LRU after overwrite pc->mem_cgroup. > > > > > > > > So, reusing SwapCache code with renaming for fix. > > > > > > > > Note: a page on pagevec(LRU). > > > > > > > > If a page is not PageLRU(page) but on pagevec(LRU), it may be added to LRU > > > > while we overwrite page->mapping. But in that case, PCG_USED bit of > > > > the page_cgroup is not set and the page_cgroup will not be added to > > > > wrong memcg's LRU. So, this patch's logic will work fine. > > > > (It has been tested with SwapCache.) > > > > > > > As for SwapCache, mem_cgroup_lru_add_after_commit() will be allways called, > > > and it will link the page to LRU. But, if I read this patch correctly, > > > a page cache on pagevec may not be added to a *proper* memcg's LRU. > > > > > > lru_add_drain() mem_cgroup_cache_charge() > > > ---------------------------------------------------------- > > > if (!PageLRU()) > > > SetPageLRU() > > > add_page_to_lru_list() > > > mem_cgroup_add_lru_list() > > > -> do nothing > > > mem_cgroup_charge_common() > > > mem_cgroup_commit_charge() > > > -> set PCG_USED > > > > > > > Hmm, yes, that's possible case. > > > > So, PageLRU() && !PcgAcctLru(pc) should be checked after commit ? > > > I think so, as mem_cgroup_lru_add_after_commit() does. > > > I think we can add optimization later (add per-memcg-lru-pegecgrou-vec or some) > > > In current mmotm, fuse uses replace_page_cache(), which uses mem_cgroup_(prepare|end)_migration(), > so I think we can handle this problem in a different way instead of changing > mem_cgroup_cache_charge(), which I think is a fast-path operation. > Hmm, but a fix for 2.6.37 is a problem... _AND_ this kind of breakage by some code can be happen, again. I think we need a check in this path. Let's try and see overheads. Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>