From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx123.postini.com [74.125.245.123]) by kanga.kvack.org (Postfix) with SMTP id A1F246B13F2 for ; Fri, 10 Feb 2012 15:39:04 -0500 (EST) Received: by vcbf13 with SMTP id f13so1837880vcb.14 for ; Fri, 10 Feb 2012 12:39:03 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <1328905759.25989.57.camel@laptop> References: <1327572121-13673-1-git-send-email-gilad@benyossef.com> <1327591185.2446.102.camel@twins> <20120201170443.GE6731@somewhere.redhat.com> <4F2AAEB9.9070302@tilera.com> <1328899148.25989.38.camel@laptop> <1328905759.25989.57.camel@laptop> Date: Fri, 10 Feb 2012 22:39:02 +0200 Message-ID: Subject: Re: [v7 0/8] Reduce cross CPU IPI interference From: Gilad Ben-Yossef Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Peter Zijlstra Cc: Chris Metcalf , Frederic Weisbecker , linux-kernel@vger.kernel.org, Christoph Lameter , linux-mm@kvack.org, Pekka Enberg , Matt Mackall , Sasha Levin , Rik van Riel , Andi Kleen , Mel Gorman , Andrew Morton , Alexander Viro , Avi Kivity , Michal Nazarewicz , Kosaki Motohiro , Milton Miller On Fri, Feb 10, 2012 at 10:29 PM, Peter Zijlstra w= rote: > On Fri, 2012-02-10 at 22:13 +0200, Gilad Ben-Yossef wrote: >> My current understanding is that if I have a real time task and wish it >> have a deterministic performance time, you should call mlockall() to loc= k >> the program data and text into physical memory so that =A0a =A0less ofte= n taken >> branch or access to a new data region will not result in a page fault. >> >> You still have to worry about TLB misses on non hardware page table >> walk architecture, but at least everything is in the =A0page tables >> >> If there is a better way to do this? I'm always happy to learn new >> ways to do things. :-) > > A rt application usually consists of a lot of non-rt parts and a usually > relatively small rt part. Using mlockall() pins the entire application > into memory, which while on the safe side is very often entirely too > much. > > The alternative method is to only mlock the text and data used by the rt > part. You need to be aware of what text runs in your rt part anyway, > since you need to make sure it is in fact deterministic code. > > One of the ways of achieving this is using a special linker section for > your vetted rt code and mlock()'ing only that text section. > > On thread creation, provide a custom allocated (and mlock()'ed) stack > etc.. > > Basically, if you can't tell a-priory what code is part of your rt part, > you don't have an rt part ;-) > That I can totally agree with. I guess mlockall() is still useful as a kind of hack for lazy people, although if you say that this kind of laziness does not really mix well with real time programming I will tend to agree... :-) Gilad --=20 Gilad Ben-Yossef Chief Coffee Drinker gilad@benyossef.com Israel Cell: +972-52-8260388 US Cell: +1-973-8260388 http://benyossef.com "If you take a class in large-scale robotics, can you end up in a situation where the homework eats your dog?" =A0-- Jean-Baptiste Queru -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org