Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753436Ab0F1BcP (ORCPT ); Sun, 27 Jun 2010 21:32:15 -0400 Received: from fgwmail7.fujitsu.co.jp ([192.51.44.37]:47239 "EHLO fgwmail7.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752162Ab0F1BcF (ORCPT ); Sun, 27 Jun 2010 21:32:05 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 From: KOSAKI Motohiro To: Christoph Lameter Subject: Re: [PATCH 1/2] vmscan: shrink_slab() require number of lru_pages, not page order Cc: kosaki.motohiro@jp.fujitsu.com, LKML , linux-mm , Andrew Morton , Mel Gorman , Rik van Riel , Minchan Kim , Johannes Weiner 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 X-Mailer: Becky! ver. 2.50.07 [ja] Date: Mon, 28 Jun 2010 10:32:00 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1317 Lines: 39 > 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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/