From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753593Ab2FSCHo (ORCPT ); Mon, 18 Jun 2012 22:07:44 -0400 Received: from mail-pz0-f46.google.com ([209.85.210.46]:49458 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752227Ab2FSCHl (ORCPT ); Mon, 18 Jun 2012 22:07:41 -0400 Message-ID: <4FDFDEE8.2030108@gmail.com> Date: Tue, 19 Jun 2012 10:07:36 +0800 From: "gnehzuil.lzheng@gmail.com" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:8.0) Gecko/20111124 Thunderbird/8.0 MIME-Version: 1.0 To: Rob Landley CC: Jens Axboe , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: Why does ionice(1) ban the user to set back to 'none' class? References: <20120618114841.GA4855@gmail.com> <4FDF3AAA.9020101@landley.net> In-Reply-To: <4FDF3AAA.9020101@landley.net> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/18/2012 10:26 PM, Rob Landley wrote: > On 06/18/2012 06:48 AM, Zheng Liu wrote: >> Hi Jens, >> >> I meet a problem when I use ionice(1) to adjust a process's io priority. >> I do the following operations: >> >> $ ionice -p${pid} >> none: prio 0 >> $ ionice -p${pid} -c2 -n4 >> $ ionice -p${pid} >> best-effort: prio 4 >> $ ionice -p${pid} -c0 -n0 >> $ ionice -p${pid} >> best-effort: prio 0 >> >> So I cannot set scheduling class back to 'none'. If I call ioprio_set(2) >> directly, it will be fine. But if I use ionice(1), I cannot change it. I >> read the docs about ionice in [1]. I notice this code: >> >> switch (ioprio_class) { >> case IOPRIO_CLASS_NONE: >> ioprio_class = IOPRIO_CLASS_BE; >> ^^^^^^^^^^^^^^^^ >> *It means that we cannot set back to none.* >> break; >> case IOPRIO_CLASS_RT: >> case IOPRIO_CLASS_BE: >> break; >> case IOPRIO_CLASS_IDLE: >> ioprio = 7; >> break; >> default: >> printf("bad prio class %d\n", ioprio_class); >> return 1; >> } >> >> My question is why we need to ban the user to set back to 'none'. Is there >> some reasons? Thank you. > > Since I'm CC'd, I'll explicitly say I haven't a clue why it does this. Thank you all the same. :-) Regards, Zheng