From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <49368DAF.9060206@redhat.com> Date: Wed, 03 Dec 2008 08:46:23 -0500 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH] vmscan: improve reclaim throuput to bail out patch References: <49316CAF.2010006@redhat.com> <20081130150849.8140.KOSAKI.MOTOHIRO@jp.fujitsu.com> <20081203140419.1D44.KOSAKI.MOTOHIRO@jp.fujitsu.com> In-Reply-To: <20081203140419.1D44.KOSAKI.MOTOHIRO@jp.fujitsu.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: KOSAKI Motohiro Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, mel@csn.ul.ie List-ID: KOSAKI Motohiro wrote: > Hi > > I evaluate rvr bailout and skip-freeing patch in this week conteniously. > I'd like to dump first output here. > > > > Rik, could you please review following? > == > vmscan bail out patch move nr_reclaimed variable to struct scan_control. > Unfortunately, indirect access can easily happen cache miss. > More unfortunately, Some architecture (e.g. ia64) don't access global > variable so fast. That is amazing. Especially considering that the scan_control is a local variable on the stack. > if heavy memory pressure happend, that's ok. > cache miss already plenty. it is not observable. > > but, if memory pressure is lite, performance degression is obserbable. > about 4-5% degression. > > Then, this patch introduce temporal local variable. > OK. the degression is disappeared. I can't argue with the numbers, though :) Maybe all the scanning we do ends up evicting the cache lines with the scan_control struct in it from the fast part of the CPU cache? > Signed-off-by: KOSAKI Motohiro Acked-by: Rik van Riel -- All rights reversed. -- 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