lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Fri, 17 May 2013 16:39:02 -0400 From: Johannes Weiner <hannes@...xchg.org> To: Mel Gorman <mgorman@...e.de> Cc: Alexey Lyahkov <alexey.lyashkov@...il.com>, Andrew Perepechko <anserper@...ru>, Robin Dong <sanbai@...bao.com>, Theodore Tso <tytso@....edu>, Andrew Morton <akpm@...ux-foundation.org>, Hugh Dickins <hughd@...gle.com>, Rik van Riel <riel@...hat.com>, Bernd Schubert <bernd.schubert@...tmail.fm>, David Howells <dhowells@...hat.com>, Trond Myklebust <Trond.Myklebust@...app.com>, Linux-fsdevel <linux-fsdevel@...r.kernel.org>, Linux-ext4 <linux-ext4@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, Linux-mm <linux-mm@...ck.org> Subject: Re: [PATCH 3/5] mm: Activate !PageLRU pages on mark_page_accessed if page is on local pagevec On Fri, May 17, 2013 at 10:48:05AM +0100, Mel Gorman wrote: > If a page is on a pagevec then it is !PageLRU and mark_page_accessed() > may fail to move a page to the active list as expected. Now that the LRU > is selected at LRU drain time, mark pages PageActive if they are on the > local pagevec so it gets moved to the correct list at LRU drain time. > Using a debugging patch it was found that for a simple git checkout based > workload that pages were never added to the active file list in practice > but with this patch applied they are. > > before after > LRU Add Active File 0 750583 > LRU Add Active Anon 2640587 2702818 > LRU Add Inactive File 8833662 8068353 > LRU Add Inactive Anon 207 200 > > Note that only pages on the local pagevec are considered on purpose. A > !PageLRU page could be in the process of being released, reclaimed, migrated > or on a remote pagevec that is currently being drained. Marking it PageActive > is vunerable to races where PageLRU and Active bits are checked at the > wrong time. Page reclaim will trigger VM_BUG_ONs but depending on when the > race hits, it could also free a PageActive page to the page allocator and > trigger a bad_page warning. Similarly a potential race exists between a > per-cpu drain on a pagevec list and an activation on a remote CPU. > > lru_add_drain_cpu > __pagevec_lru_add > lru = page_lru(page); > mark_page_accessed > if (PageLRU(page)) > activate_page > else > SetPageActive > SetPageLRU(page); > add_page_to_lru_list(page, lruvec, lru); > > In this case a PageActive page is added to the inactivate list and later the > inactive/active stats will get skewed. While the PageActive checks in vmscan > could be removed and potentially dealt with, a skew in the statistics would > be very difficult to detect. Hence this patch deals just with the common case > where a page being marked accessed has just been added to the local pagevec. > > Signed-off-by: Mel Gorman <mgorman@...e.de> Acked-by: Johannes Weiner <hannes@...xchg.org> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists