From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <46CB55A8.4030501@redhat.com> Date: Tue, 21 Aug 2007 17:14:16 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [RFC 0/7] Postphone reclaim laundry to write at high water marks References: <20070820215040.937296148@sgi.com> <46CB01B7.3050201@redhat.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed 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, akpm@linux-foundation.org, dkegel@google.com, Peter Zijlstra , David Miller , Nick Piggin List-ID: Christoph Lameter wrote: > On Tue, 21 Aug 2007, Rik van Riel wrote: > >> Christoph Lameter wrote: >> >>> 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. >> That sounds like a horrendously bad idea. While one process >> is busy freeing all the non dirty pages, other processes can >> allocate those pages, leaving you with no memory to free up >> the dirty pages! > > What is preventing that from occurring right now? If the dirty pags are > aligned in the right way you can have the exact same situation. For one, dirty page writeout is done even when free memory is low. The kernel will dig into the PF_MEMALLOC reserves, instead of deciding not to do writeout unless there is lots of free memory. Secondly, why would you want to recreate this worst case on purpose every time the pageout code runs? -- Politics is the struggle between those who want to make their country the best in the world, and those who believe it already is. Each group calls the other unpatriotic. -- 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