From mboxrd@z Thu Jan 1 00:00:00 1970 Message-Id: <20070820215040.937296148@sgi.com> Date: Mon, 20 Aug 2007 14:50:40 -0700 From: Christoph Lameter Subject: [RFC 0/7] Postphone reclaim laundry to write at high water marks Sender: owner-linux-mm@kvack.org Return-Path: To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, dkegel@google.com, Peter Zijlstra , David Miller , Nick Piggin List-ID: 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. -- -- 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