From: KOSAKI Motohiro Subject: Re: [PATCH, RFC 0/3] Introduce new O_HOT and O_COLD flags Date: Sat, 21 Apr 2012 19:56:05 -0400 Message-ID: References: <1334863211-19504-1-git-send-email-tytso@mit.edu> <4F912880.70708@panasas.com> <1334919662.5879.23.camel@dabdike> <1334932928.13001.11.camel@dabdike> <20120420145856.GC24486@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: James Bottomley , Lukas Czerner , Boaz Harrosh , linux-fsdevel@vger.kernel.org, Ext4 Developers List , linux-mm@kvack.org To: "Ted Ts'o" Return-path: Received: from mail-pz0-f42.google.com ([209.85.210.42]:58058 "EHLO mail-pz0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751548Ab2DUX40 convert rfc822-to-8bit (ORCPT ); Sat, 21 Apr 2012 19:56:26 -0400 In-Reply-To: <20120420145856.GC24486@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Fri, Apr 20, 2012 at 10:58 AM, Ted Ts'o wrote: > On Fri, Apr 20, 2012 at 06:42:08PM +0400, James Bottomley wrote: >> >> I'm not at all wedded to O_HOT and O_COLD; I think if we establish a >> hint hierarchy file->page cache->device then we should, of course, >> choose the best API and naming scheme for file->page cache. =A0The o= nly >> real point I was making is that we should tie in the page cache, and >> currently it only knows about "hot" and "cold" pages. > > The problem is that "hot" and "cold" will have different meanings fro= m > the perspective of the file system versus the page cache. =A0The file > system may consider a file "hot" if it is accessed frequently --- > compared to the other 2 TB of data on that HDD. =A0The memory subsyst= em > will consider a page "hot" compared to what has been recently accesse= d > in the 8GB of memory that you might have your system. =A0Now consider > that you might have a dozen or so 2TB disks that each have their "hot= " > areas, and it's not at all obvious that just because a file, or even > part of a file is marked "hot", that it deserves to be in memory at > any particular point in time. So, this have intentionally different meanings I have no seen a reason = why fs uses hot/cold words. It seems to bring a confusion. But I don't know full story of this feature and I might be overlooking something. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html