From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [RFC 0/7] Postphone reclaim laundry to write at high water marks From: Peter Zijlstra In-Reply-To: <20070820215040.937296148@sgi.com> References: <20070820215040.937296148@sgi.com> Content-Type: text/plain Date: Tue, 21 Aug 2007 12:36:26 +0200 Message-Id: <1187692586.6114.211.camel@twins> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On Mon, 2007-08-20 at 14:50 -0700, Christoph Lameter wrote: > One of the problems with reclaim writeout is that it occurs when memory in a > zone is low. A particular bad problem can occur if memory in a zone is > already low and now the first page that we encounter during reclaim is dirty. > So the writeout function is called without the filesystem or device having > much of a reserve that would allow further allocations. Triggering writeout > of dirty pages early does not improve the memory situation since the actual > writeout of the page is a relatively long process. The call to writepage > will therefore not improve the low memory situation but make it worse > because extra memory may be needed to get the device to write the page. > > This patchset fixes that issue by: > > 1. First reclaiming non dirty pages. Dirty pages are deferred until reclaim > has reestablished the high marks. Then all the dirty pages (the laundry) > is written out. > > 2. Reclaim is essentially complete during the writeout phase. So we remove > PF_MEMALLOC and allow recursive reclaim if we still run into trouble > during writeout. This almost insta-OOMs with anonymous workloads. -- 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