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 20FCB6B0071 for ; Tue, 23 Nov 2010 04:02:07 -0500 (EST) Received: from m2.gw.fujitsu.co.jp ([10.0.50.72]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id oAN921sW000622 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Tue, 23 Nov 2010 18:02:02 +0900 Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 9F6A645DD76 for ; Tue, 23 Nov 2010 18:02:01 +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 82F8745DD73 for ; Tue, 23 Nov 2010 18:02:01 +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 71C4E1DB803A for ; Tue, 23 Nov 2010 18:02:01 +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 2B2691DB8038 for ; Tue, 23 Nov 2010 18:02:01 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [RFC 1/2] deactive invalidated pages 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 Date: Tue, 23 Nov 2010 18:02:00 +0900 (JST) Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: kosaki.motohiro@jp.fujitsu.com, Andrew Morton , linux-mm , LKML , Peter Zijlstra , Rik van Riel , Johannes Weiner , Nick Piggin List-ID: > 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, 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/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org