From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx132.postini.com [74.125.245.132]) by kanga.kvack.org (Postfix) with SMTP id 7C2A56B0005 for ; Sat, 23 Feb 2013 20:47:03 -0500 (EST) Received: from /spool/local by e8.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sat, 23 Feb 2013 20:47:02 -0500 Received: from d01relay01.pok.ibm.com (d01relay01.pok.ibm.com [9.56.227.233]) by d01dlp03.pok.ibm.com (Postfix) with ESMTP id 9A288C9001B for ; Sat, 23 Feb 2013 20:46:59 -0500 (EST) Received: from d01av02.pok.ibm.com (d01av02.pok.ibm.com [9.56.224.216]) by d01relay01.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r1O1kx8S326646 for ; Sat, 23 Feb 2013 20:46:59 -0500 Received: from d01av02.pok.ibm.com (loopback [127.0.0.1]) by d01av02.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r1O1kxQm005066 for ; Sat, 23 Feb 2013 22:46:59 -0300 Message-ID: <5129710F.6060804@linux.vnet.ibm.com> Date: Sat, 23 Feb 2013 17:46:55 -0800 From: Dave Hansen MIME-Version: 1.0 Subject: Re: [PATCH 1/2] mm: fadvise: fix POSIX_FADV_DONTNEED References: <1361660281-22165-1-git-send-email-psusi@ubuntu.com> <1361660281-22165-2-git-send-email-psusi@ubuntu.com> In-Reply-To: <1361660281-22165-2-git-send-email-psusi@ubuntu.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Phillip Susi Cc: linux-mm@kvack.org On 02/23/2013 02:58 PM, Phillip Susi wrote: > 2) Discarding pages under low cache pressure is a waste > 3) It was useless on files being written, and thus full of dirty pages > > Now we just move the pages to the inactive list so they will be reclaimed > sooner. Folks actually use this in practice to flush the page cache out: http://git.sr71.net/?p=eyefi-config.git;a=blob;f=eyefi-linux.c;h=b77a891995109f6caa288925a13985cc495d7b2d;hb=HEAD#l62 I have really good reasons for really wanting to be _rid_ of the page cache no matter how much memory pressure there is. I've seen people at IBM using this to ensure that they stay out of memory reclaim completely. I don't completely agree with the approach, but this would completely ruin their performance since the VM-initiated writeout is so relatively slow for them. I think this patch is a really bad idea. If you want the behavior you're proposing, I'd suggest using another flag. -- 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/ . Don't email: email@kvack.org