From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <45B9F26D.5090107@yahoo.com.au> Date: Fri, 26 Jan 2007 23:22:05 +1100 From: Nick Piggin MIME-Version: 1.0 Subject: Re: [RFC 0/8] Use ZVCs for accurate writeback ratio determination References: <20070126054153.10564.43218.sendpatchset@schroedinger.engr.sgi.com> In-Reply-To: <20070126054153.10564.43218.sendpatchset@schroedinger.engr.sgi.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: akpm@osdl.org, Peter Zijlstra , linux-mm@kvack.org, Nikita Danilov , Andi Kleen List-ID: Christoph Lameter wrote: > The determination of the dirty ratio to determine writeback behavior > is currently based on the number of total pages on the system. > > However, not all pages in the system may be dirtied. Thus the ratio > is always too low and can never reach 100%. The ratio may be > particularly skewed if large hugepage allocations, slab allocations > or device driver buffers make large sections of memory not available > anymore. In that case we may get into a situation in which f.e. the > background writeback ratio of 40% cannot be reached anymore which > leads to undesired writeback behavior. > > This patchset fixes that issue by determining the ratio based > on the actual pages that may potentially be dirty. These are > the pages on the active and the inactive list plus free pages. So you no longer account for reclaimable slab allocations, which would be a significant change on some workloads. Any reason for that? -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com -- 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