From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 96FE86B01B2 for ; Sun, 27 Jun 2010 21:32:04 -0400 (EDT) Received: from m3.gw.fujitsu.co.jp ([10.0.50.73]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o5S1W1Au031006 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Mon, 28 Jun 2010 10:32:02 +0900 Received: from smail (m3 [127.0.0.1]) by outgoing.m3.gw.fujitsu.co.jp (Postfix) with ESMTP id B186F45DD77 for ; Mon, 28 Jun 2010 10:32:01 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (s3.gw.fujitsu.co.jp [10.0.50.93]) by m3.gw.fujitsu.co.jp (Postfix) with ESMTP id 921F145DE4D for ; Mon, 28 Jun 2010 10:32:01 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id 7CEEC1DB8037 for ; Mon, 28 Jun 2010 10:32:01 +0900 (JST) Received: from ml14.s.css.fujitsu.com (ml14.s.css.fujitsu.com [10.249.87.104]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id 2EF721DB803B for ; Mon, 28 Jun 2010 10:32:01 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [PATCH 1/2] vmscan: shrink_slab() require number of lru_pages, not page order In-Reply-To: References: <20100625201915.8067.A69D9226@jp.fujitsu.com> Message-Id: <20100628102342.386D.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Mon, 28 Jun 2010 10:32:00 +0900 (JST) Sender: owner-linux-mm@kvack.org To: Christoph Lameter Cc: kosaki.motohiro@jp.fujitsu.com, LKML , linux-mm , Andrew Morton , Mel Gorman , Rik van Riel , Minchan Kim , Johannes Weiner List-ID: > On Fri, 25 Jun 2010, KOSAKI Motohiro wrote: > > > Fix simple argument error. Usually 'order' is very small value than > > lru_pages. then it can makes unnecessary icache dropping. > > This is going to reduce the delta that is added to shrinker->nr > significantly thereby increasing the number of times that shrink_slab() is > called. Yup. But, Smaller shrink -> only makes retry Bigger shrink -> makes unnecessary icache/dcache drop. it can bring mysterious low performance. > What does the "lru_pages" parameter do in shrink_slab()? Looks > like its only role is as a divison factor in a complex calculation of > pages to be scanned. Yes. scanned/lru_pages ratio define basic shrink_slab puressure strength. So, If you intentionally need bigger slab pressure, bigger scanned parameter passing is better rather than mysterious 'order' parameter. > > do_try_to_free_pages passes 0 as "lru_pages" to shrink_slab() when trying > to do cgroup lru scans. Why is that? ? When cgroup lru scans, do_try_to_free_pages() don't call shrink_slab(). -- 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