From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Ray Bryant" Subject: Re: [PATCH 0/4] Demand faunting for huge pages Date: Thu, 18 Aug 2005 10:29:00 -0500 References: <1124304966.3139.37.camel@localhost.localdomain> <20050817210431.GR3996@wotan.suse.de> <20050818003302.GE7103@localhost.localdomain> In-Reply-To: <20050818003302.GE7103@localhost.localdomain> MIME-Version: 1.0 Message-ID: <200508181029.01238.raybry@mpdtxmail.amd.com> Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: owner-linux-mm@kvack.org Return-Path: To: David Gibson Cc: Andi Kleen , Adam Litke , linux-mm@kvack.org, christoph@lameter.com, kenneth.w.chen@intel.com, akpm@osdl.org List-ID: On Wednesday 17 August 2005 19:33, David Gibson wrote: > > Strict accounting leads to nicer behaviour in some cases - you'll tend > to die early rather than late - but it seems an awful lot of work for > a fairly small improvement in behaviour. > The last time we went around on this (April 2004?) Andrew thought that adding demand allocation for hugetlb pages without strict accounting was effectively an ABI change -- in the current approach the mmap() will fail if you ask for too many hugetlb pages whilst in the demand fault approach you will get SIGBUS at a later point in time. At one time this was considered serious enough to fix. Andy Whitcroft provided some code for the patch that Ken and I did back in April 2004 time frame. I can't find that one but the following patch from Christoph Lameter appears to be the code. The idea is that at mmap() time a strict reservation is made that guarantees the necessary number of hugetlb pages is available. http://marc.theaimsgroup.com/?l=linux-kernel&m=109842250714489&w=2 -- Ray Bryant AMD Performance Labs Austin, Tx 512-602-0038 (o) 512-507-7807 (c) -- 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/ . Don't email: email@kvack.org