From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id 5CE1B6B0089 for ; Tue, 23 Nov 2010 03:45:00 -0500 (EST) Received: by iwn10 with SMTP id 10so1081051iwn.14 for ; Tue, 23 Nov 2010 00:44:59 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20101123165240.7BC2.A69D9226@jp.fujitsu.com> References: <20101122143817.E242.A69D9226@jp.fujitsu.com> <20101123165240.7BC2.A69D9226@jp.fujitsu.com> Date: Tue, 23 Nov 2010 17:44:57 +0900 Message-ID: Subject: Re: [RFC 1/2] deactive invalidated pages From: Minchan Kim Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: 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. -- Kind regards, Minchan Kim -- 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