From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 21 Aug 2007 14:03:28 -0700 (PDT) From: Christoph Lameter Subject: Re: [RFC 0/7] Postphone reclaim laundry to write at high water marks In-Reply-To: <200708211051.36569.dave.mccracken@oracle.com> Message-ID: References: <20070820215040.937296148@sgi.com> <200708211051.36569.dave.mccracken@oracle.com> MIME-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="-1700579579-1839598108-1187730208=:3082" Sender: owner-linux-mm@kvack.org Return-Path: To: Dave McCracken Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: ---1700579579-1839598108-1187730208=:3082 Content-Type: TEXT/PLAIN; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE On Tue, 21 Aug 2007, Dave McCracken wrote: > On Monday 20 August 2007, Christoph Lameter wrote: > > 1. First reclaiming non dirty pages. Dirty pages are deferred until rec= laim > > =A0 =A0has reestablished the high marks. Then all the dirty pages (the = laundry) > > =A0 =A0is written out. >=20 > I don't buy it. What happens when there aren't enough clean pages in the= =20 > system to achieve the high water mark? I'm guessing we'd get a quick OOM= (as=20 > observed by Peter). We reclaim the clean pages that there are (removing the executable=20 pages from memory) and then we do writeback. The quick OOM is due to throttling not working right AFAIK. > > 2. Reclaim is essentially complete during the writeout phase. So we rem= ove > > =A0 =A0PF_MEMALLOC and allow recursive reclaim if we still run into tro= uble > > =A0 =A0during writeout. >=20 > You're assuming the system is static and won't allocate new pages behind = your=20 > back. We could be back to critically low memory before the write happens= =2E Yes and that occurs now too. > More broadly, we need to be proactive about getting dirty pages cleaned b= efore=20 > they consume the system. Deferring the write just makes it harder to kee= p=20 > up. Cleaning dirty pages through writeout consumes memory. Writing dirty pages= =20 out early makes the memory situation even worse. ---1700579579-1839598108-1187730208=:3082-- -- 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