From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id A2EFF6B004A for ; Tue, 30 Nov 2010 09:03:50 -0500 (EST) Received: by ywg4 with SMTP id 4so487150ywg.14 for ; Tue, 30 Nov 2010 06:03:48 -0800 (PST) Date: Tue, 30 Nov 2010 23:03:33 +0900 From: Minchan Kim Subject: Re: [PATCH 2/3] Reclaim invalidated page ASAP Message-ID: <20101130140333.GB1528@barrios-desktop> References: <053e6a3308160a8992af5a47fb4163796d033b08.1291043274.git.minchan.kim@gmail.com> <20101129165706.GH13268@csn.ul.ie> <20101129224130.GA1989@barrios-desktop> <20101130112041.GC15564@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20101130112041.GC15564@cmpxchg.org> Sender: owner-linux-mm@kvack.org To: Johannes Weiner Cc: Mel Gorman , Andrew Morton , linux-mm , LKML , Ben Gamari , Wu Fengguang , KOSAKI Motohiro , Nick Piggin List-ID: On Tue, Nov 30, 2010 at 12:20:41PM +0100, Johannes Weiner wrote: > On Tue, Nov 30, 2010 at 07:41:30AM +0900, Minchan Kim wrote: > > > diff --git a/mm/swap.c b/mm/swap.c > > index 19e0812..1f1f435 100644 > > --- a/mm/swap.c > > +++ b/mm/swap.c > > @@ -275,28 +275,51 @@ void add_page_to_unevictable_list(struct page *page) > > * into inative list's head. Because the VM expects the page would > > * be writeout by flusher. The flusher's writeout is much effective > > * than reclaimer's random writeout. > > + * > > + * If the page isn't page_mapped and dirty/writeback, the page > > + * could reclaim asap using PG_reclaim. > > + * > > + * 1. active, mapped page -> none > > + * 2. active, dirty/writeback page -> inactive, head, PG_reclaim > > + * 3. inactive, mapped page -> none > > + * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim > > + * 5. Others -> none > > + * > > + * In 4, why it moves inactive's head, the VM expects the page would > > + * be writeout by flusher. The flusher's writeout is much effective than > > + * reclaimer's random writeout. > > */ > > static void __lru_deactivate(struct page *page, struct zone *zone) > > { > > int lru, file; > > - unsigned long vm_flags; > > + int active = 0; > > vm_flags is never used in this series. It's garbage in my old version which is used page_referenced. > > > - if (!PageLRU(page) || !PageActive(page)) > > + if (!PageLRU(page)) > > return; > > - > > /* Some processes are using the page */ > > if (page_mapped(page)) > > return; > > - > > - file = page_is_file_cache(page); > > - lru = page_lru_base_type(page); > > - del_page_from_lru_list(zone, page, lru + LRU_ACTIVE); > > - ClearPageActive(page); > > - ClearPageReferenced(page); > > - add_page_to_lru_list(zone, page, lru); > > - __count_vm_event(PGDEACTIVATE); > > - > > - update_page_reclaim_stat(zone, page, file, 0); > > + if (PageActive(page)) > > + active = 1; > > active = PageActive(page) Will fix. > > > + if (PageWriteback(page) || PageDirty(page)) { > > + /* > > + * PG_reclaim could be raced with end_page_writeback > > + * It can make readahead confusing. But race window > > + * is _really_ small and it's non-critical problem. > > + */ > > + SetPageReclaim(page); > > + > > + file = page_is_file_cache(page); > > + lru = page_lru_base_type(page); > > + del_page_from_lru_list(zone, page, lru + active); > > + ClearPageActive(page); > > + ClearPageReferenced(page); > > + add_page_to_lru_list(zone, page, lru); > > + if (active) > > + __count_vm_event(PGDEACTIVATE); > > + update_page_reclaim_stat(zone, page, file, 0); > > + } > > If we lose the race with writeback, the completion handler won't see > PG_reclaim, won't move the page, and we have an unwanted clean cache > page on the active list. Given the pagevec caching of those pages it > could be rather likely that IO completes before the above executes. > > Shouldn't this be > > if (PageWriteback() || PageDirty()) { > SetPageReclaim() > move_to_inactive_head() > } else { > move_to_inactive_tail() > } > > instead? Fair enough. Thanks, Hannes. > > Hannes -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org