From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759894Ab1LPPSJ (ORCPT ); Fri, 16 Dec 2011 10:18:09 -0500 Received: from mx1.redhat.com ([209.132.183.28]:10648 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755763Ab1LPPSD (ORCPT ); Fri, 16 Dec 2011 10:18:03 -0500 Date: Fri, 16 Dec 2011 16:17:31 +0100 From: Johannes Weiner To: Mel Gorman Cc: Andrew Morton , Andrea Arcangeli , Minchan Kim , Dave Jones , Jan Kara , Andy Isaacson , Rik van Riel , Nai Xia , Linux-MM , LKML Subject: Re: [PATCH 11/11] mm: Isolate pages for immediate reclaim on their own LRU Message-ID: <20111216151703.GA12817@redhat.com> References: <1323877293-15401-1-git-send-email-mgorman@suse.de> <1323877293-15401-12-git-send-email-mgorman@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1323877293-15401-12-git-send-email-mgorman@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 14, 2011 at 03:41:33PM +0000, Mel Gorman wrote: > It was observed that scan rates from direct reclaim during tests > writing to both fast and slow storage were extraordinarily high. The > problem was that while pages were being marked for immediate reclaim > when writeback completed, the same pages were being encountered over > and over again during LRU scanning. > > This patch isolates file-backed pages that are to be reclaimed when > clean on their own LRU list. Excuse me if I sound like a broken record, but have those observations of high scan rates persisted with the per-zone dirty limits patchset? In my tests with pzd, the scan rates went down considerably together with the immediate reclaim / vmscan writes. Our dirty limits are pretty low - if reclaim keeps shuffling through dirty pages, where are the 80% reclaimable pages?! To me, this sounds like the unfair distribution of dirty pages among zones again. Is there are a different explanation that I missed? PS: It also seems a bit out of place in this series...?