Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751949Ab0KWJCG (ORCPT ); Tue, 23 Nov 2010 04:02:06 -0500 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:51302 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751022Ab0KWJCD (ORCPT ); Tue, 23 Nov 2010 04:02:03 -0500 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 From: KOSAKI Motohiro To: Minchan Kim Subject: Re: [RFC 1/2] deactive invalidated pages Cc: kosaki.motohiro@jp.fujitsu.com, Andrew Morton , linux-mm , LKML , Peter Zijlstra , Rik van Riel , Johannes Weiner , Nick Piggin In-Reply-To: References: <20101123165240.7BC2.A69D9226@jp.fujitsu.com> Message-Id: <20101123175948.7BD1.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: Tue, 23 Nov 2010 18:02:00 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1926 Lines: 47 > On Tue, Nov 23, 2010 at 5:01 PM, KOSAKI Motohiro > wrote: > >> Hi KOSAKI, > >> > >> 2010/11/23 KOSAKI Motohiro : > >> >> By Other approach, app developer uses POSIX_FADV_DONTNEED. > >> >> But it has a problem. If kernel meets page is writing > >> >> during invalidate_mapping_pages, it can't work. > >> >> It is very hard for application programmer to use it. > >> >> Because they always have to sync data before calling > >> >> fadivse(..POSIX_FADV_DONTNEED) to make sure the pages could > >> >> be discardable. At last, they can't use deferred write of kernel > >> >> so that they could see performance loss. > >> >> (http://insights.oetiker.ch/linux/fadvise.html) > >> > > >> > If rsync use the above url patch, we don't need your patch. > >> > fdatasync() + POSIX_FADV_DONTNEED should work fine. > >> > >> It works well. But it needs always fdatasync before calling fadvise. > >> For small file, it hurt performance since we can't use the deferred write. > > > > I doubt rsync need to call fdatasync. Why? > > > > If rsync continue to do following loop, some POSIX_FADV_DONTNEED > > may not drop some dirty pages. But they can be dropped at next loop's > > POSIX_FADV_DONTNEED. Then, It doesn't make serious issue. > > > > 1) read > > 2) write > > 3) POSIX_FADV_DONTNEED > > 4) goto 1 > > fadvise need pair (offset and len). > if the pair in next turn is different with one's previous turn, it > couldn't be dropped. invalidate_mapping_pages() are using pagevec_lookup() and pagevec_lookup() are using radix tree lookup. Then, Even if rsync always use [0, inf) pair, I don't think it makes much slowdown. -- 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/