From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Elder Subject: Re: [PATCH, RFC 0/3] Introduce new O_HOT and O_COLD flags Date: Tue, 24 Apr 2012 11:07:57 -0500 Message-ID: <4F96CFDD.2070001@dreamhost.com> References: <1334863211-19504-1-git-send-email-tytso@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-fsdevel@vger.kernel.org, Ext4 Developers List To: Theodore Ts'o Return-path: Received: from mail.hq.newdream.net ([66.33.206.127]:57829 "EHLO mail.hq.newdream.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755787Ab2DXQHu (ORCPT ); Tue, 24 Apr 2012 12:07:50 -0400 In-Reply-To: <1334863211-19504-1-git-send-email-tytso@mit.edu> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On 04/19/2012 02:20 PM, Theodore Ts'o wrote: > As I had brought up during one of the lightning talks at the Linux > Storage and Filesystem workshop, I am interested in introducing two new > open flags, O_HOT and O_COLD. These flags are passed down to the > individual file system's inode operations' create function, and the file > system can use these flags as a hint regarding whether the file is > likely to be accessed frequently or not. > > In the future I plan to do further work on how ext4 would use these > flags, but I want to first get the ability to pass these flags plumbed > into the VFS layer and the code points for O_HOT and O_COLD reserved. Consider this: Is this a testable feature? You're proposing a hint, of course, so it could just have no effect. But let's just assume for the sake of discussion that it has been implemented. How will I (filesystem implementer) know whether I have implemented it correctly? How can the user verify that the use of these flags is producing the expected result? -Alex