On Wed, 16 Jun 2010 10:40:36 +0900 KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > On Tue, 15 Jun 2010 20:53:43 -0400 > Rik van Riel <riel@xxxxxxxxxx> wrote: > > > On 06/15/2010 08:39 PM, KAMEZAWA Hiroyuki wrote: > > > > > Hmm, or do you recommend no-dirty-page-writeback when a memcg hits limit ? > > > Maybe we'll see much swaps. > > > > > > I want to go with this for a while, changing memcg's behavior will took > > > some amounts of time, there are only a few developpers. > > > > One thing we can do, for kswapd, memcg and direct reclaim alike, > > is to tell the flusher threads to flush pages related to a pageout > > candidate page to disk. > > > > That way the reclaiming processes can wait on some disk IO to > > finish, while the flusher thread takes care of the actual flushing. > > > > That should also fix the "kswapd filesystem IO has really poor IO > > patterns" issue. > > > > There's no reason not to fix this issue the right way. > > > yes. but this patch just stops writeback. I think it's sane to ask > not to change behavior until there are some useful changes in flusher > threads. > > IMO, until flusher threads can work with I/O cgroup, memcg shoudln't > depend on it because writeback allows stealing resource without it. > BTW, copy_from_user/copy_to_user is _real_ problem, I'm afraid following much more than memcg. handle_mm_fault() -> handle_pte_fault() -> do_wp_page() -> balance_dirty_page_rate_limited() -> balance_dirty_pages() -> writeback_inodes_wbc() -> writeback_inodes_wb() -> writeback_sb_inodes() -> writeback_single_inode() -> do_writepages() -> generic_write_pages() -> write_cache_pages() // use on-stack pagevec. -> writepage() maybe much more stack consuming than memcg->writeback after vmscan.c diet. Bye. -Kame -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
