From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id 909746B00A5 for ; Mon, 18 Oct 2010 21:34:17 -0400 (EDT) Received: from m2.gw.fujitsu.co.jp ([10.0.50.72]) by fgwmail5.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o9J1YExZ018362 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Tue, 19 Oct 2010 10:34:15 +0900 Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id C3F7C45DE51 for ; Tue, 19 Oct 2010 10:34:14 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (s2.gw.fujitsu.co.jp [10.0.50.92]) by m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 962FA45DE4E for ; Tue, 19 Oct 2010 10:34:14 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 806C91DB803C for ; Tue, 19 Oct 2010 10:34:14 +0900 (JST) Received: from m107.s.css.fujitsu.com (m107.s.css.fujitsu.com [10.249.87.107]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 3ACD41DB803B for ; Tue, 19 Oct 2010 10:34:14 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [experimental][PATCH] mm,vmstat: per cpu stat flush too when per cpu page cache flushed In-Reply-To: <20101018110829.GZ30667@csn.ul.ie> References: <20101014114541.8B89.A69D9226@jp.fujitsu.com> <20101018110829.GZ30667@csn.ul.ie> Message-Id: <20101019102428.A1BF.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Tue, 19 Oct 2010 10:34:13 +0900 (JST) Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: kosaki.motohiro@jp.fujitsu.com, Shaohua Li , "linux-mm@kvack.org" , "cl@linux.com" , Andrew Morton , David Rientjes , KAMEZAWA Hiroyuki List-ID: > > Initial variable ZVC commit (df9ecaba3f1) says > > > > > [PATCH] ZVC: Scale thresholds depending on the size of the system > > > > > > The ZVC counter update threshold is currently set to a fixed value of 32. > > > This patch sets up the threshold depending on the number of processors and > > > the sizes of the zones in the system. > > > > > > With the current threshold of 32, I was able to observe slight contention > > > when more than 130-140 processors concurrently updated the counters. The > > > contention vanished when I either increased the threshold to 64 or used > > > Andrew's idea of overstepping the interval (see ZVC overstep patch). > > > > > > However, we saw contention again at 220-230 processors. So we need higher > > > values for larger systems. > > > > So, I'm worry about your patch reintroduce old cache contention issue that Christoph > > observed when run 128-256cpus system. May I ask how do you think this issue? > > It only reintroduces the overhead while kswapd is awake and the system is in danger > of accidentally allocating all of its pages. Yes, it's slower but it's > less risky. When we have rich storage and running IO intensive workload, kswapd are almost always awake ;) However, yes, your approach is less risky. -- 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