From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id C18E66B0055 for ; Thu, 12 Mar 2009 08:19:21 -0400 (EDT) From: Robin Getz Subject: Re: [PATCH] NOMMU: Pages allocated to a ramfs inode's pagecache may get wrongly discarded Date: Thu, 12 Mar 2009 08:19:08 -0400 References: <20090311170207.1795cad9.akpm@linux-foundation.org> <28c262360903111735s2b0c43a3pd48fcf8d55416ae3@mail.gmail.com> <20090312100049.43A3.A69D9226@jp.fujitsu.com> In-Reply-To: <20090312100049.43A3.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-ID: <200903120819.08724.rgetz@blackfin.uclinux.org> Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: Minchan Kim , Andrew Morton , dhowells@redhat.com, torvalds@linux-foundation.org, peterz@infradead.org, Enrik.Berkhan@ge.com, uclinux-dev@uclinux.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Johannes Weiner , Rik van Riel , Lee Schermerhorn List-ID: On Wed 11 Mar 2009 21:04, KOSAKI Motohiro pondered: > Hi > > > >> Page reclaim shouldn't be even attempting to reclaim or write back > > >> ramfs pagecache pages - reclaim can't possibly do anything with > > >> these pages! > > >> > > >> Arguably those pages shouldn't be on the LRU at all, but we haven't > > >> done that yet. > > >> > > >> Now, my problem is that I can't 100% be sure that we _ever_ > > >> implemented this properly. ?I _think_ we did, in which case > > >> we later broke it. ?If we've always been (stupidly) trying > > >> to pageout these pages then OK, I guess your patch is a > > >> suitable 2.6.29 stopgap. > > > > > > OK, I can't find any code anywhere in which we excluded ramfs pages > > > from consideration by page reclaim. ?How dumb. > > > > The ramfs considers it in just CONFIG_UNEVICTABLE_LRU case > > It that case, ramfs_get_inode calls mapping_set_unevictable. > > So, page reclaim can exclude ramfs pages by page_evictable. > > It's problem . > > Currently, CONFIG_UNEVICTABLE_LRU can't use on nommu machine > because nobody of vmscan folk havbe nommu machine. > > Yes, it is very stupid reason. _very_ welcome to tester! :) As always - if you (or any kernel developer) would like a noMMU machine to test on - please send me a private email. -- 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/ . Don't email: email@kvack.org