From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759421AbYDKI47 (ORCPT ); Fri, 11 Apr 2008 04:56:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758096AbYDKI4v (ORCPT ); Fri, 11 Apr 2008 04:56:51 -0400 Received: from wa-out-1112.google.com ([209.85.146.180]:10155 "EHLO wa-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758059AbYDKI4u (ORCPT ); Fri, 11 Apr 2008 04:56:50 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=o4KbgAEzjYaBJSOfDDM1tlxVHnwNnCaqkSkp3vCocEuG5PYPBdeuxW1fqJwlOmOARjnJTiQMScM7dA3b9pfH9MA1KfrYbnKrCmKElY7gPrWtA3IlRHBo9pCoVPXHLlUC2t1vE2duwf3Vu2toY4nvlA2gqdot8C/jg4zZmkpf8vw= Message-ID: Date: Fri, 11 Apr 2008 10:56:49 +0200 From: "Michael Kerrisk" To: "Peter Zijlstra" Subject: Re: [PATCH] proc: Add RLIMIT_RTTIME to /proc//limits Cc: "Michael Kerrisk" , "Eugene Teo" , linux-kernel@vger.kernel.org, "Neil Horman" , "Ingo Molnar" In-Reply-To: <1204212100.12120.9.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20080208145950.GA3910@kernel.sg> <1202483445.6292.1.camel@lappy> <517f3f820802280712o3d756b4fq46461b226515e1f2@mail.gmail.com> <1204212100.12120.9.camel@twins> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 28, 2008 at 5:21 PM, Peter Zijlstra wrote: > > On Thu, 2008-02-28 at 16:12 +0100, Michael Kerrisk wrote: > > Peter, > > > > Could you please provide some text describing RLIMIT_RTTIMEfor the > > getrlimit.2 man page. > > The rlimit sets a timeout in [us] for SCHED_RR and SCHED_FIFO tasks. > This time is measured between sleeps, so a schedule in RR or a > preemption in either is not a sleep - the task needs to be dequeued and > enqueued for the timer to reset. > > Upon reaching the cur limit we start giving SIGXCPU every second, upon > reaching the hard limit we give SIGKILL - matching RLIMIT_CPU. > > Time is measured in tick granularity (for now). So I have another question: why is the granularity of this rlimit microseconds? On the one hand, specifying limits down at the microsecond level seems (to my naive eye) unlikely to be useful. (But perhaps I have missed a thread where this was explained.) On the other hand, it means that on 32-bit the largest time limit we can set is ~4000 seconds, and I wonder if there are scenarios where it might be useful to have larger limits than that. Why not, for example, have a granularity of milliseconds? Cheers, Michael > > On Fri, Feb 8, 2008 at 4:10 PM, Peter Zijlstra wrote: > > > > > > On Fri, 2008-02-08 at 22:59 +0800, Eugene Teo wrote: > > > > RLIMIT_RTTIME was introduced to allow the user to set a runtime timeout on > > > > real-time tasks: http://lkml.org/lkml/2007/12/18/218. This patch updates > > > > /proc//limits with the new rlimit. > > > > > > Ah, didn't know about that file, thanks! > > > > > > > Signed-off-by: Eugene Teo > > > > > > Acked-by: Peter Zijlstra > > > > > > > > > > --- > > > > fs/proc/base.c | 1 + > > > > 1 files changed, 1 insertions(+), 0 deletions(-) > > > > > > > > diff --git a/fs/proc/base.c b/fs/proc/base.c > > > > index c59852b..dcf7be8 100644 > > > > --- a/fs/proc/base.c > > > > +++ b/fs/proc/base.c > > > > @@ -412,6 +412,7 @@ static const struct limit_names lnames[RLIM_NLIMITS] = { > > > > [RLIMIT_MSGQUEUE] = {"Max msgqueue size", "bytes"}, > > > > [RLIMIT_NICE] = {"Max nice priority", NULL}, > > > > [RLIMIT_RTPRIO] = {"Max realtime priority", NULL}, > > > > + [RLIMIT_RTTIME] = {"Max realtime timeout", "us"}, > > > > }; > > > > > > > > /* Display limits for a process */ > > > > > > -- > > > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > > > the body of a message to majordomo@vger.kernel.org > > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > Please read the FAQ at http://www.tux.org/lkml/ > > > > > > > > > > > -- Michael Kerrisk Maintainer of the Linux man-pages project http://www.kernel.org/doc/man-pages/ Want to report a man-pages bug? Look here: http://www.kernel.org/doc/man-pages/reporting_bugs.html