From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 18 Aug 2005 10:33:02 +1000 From: David Gibson Subject: Re: [PATCH 0/4] Demand faunting for huge pages Message-ID: <20050818003302.GE7103@localhost.localdomain> References: <1124304966.3139.37.camel@localhost.localdomain> <20050817210431.GR3996@wotan.suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050817210431.GR3996@wotan.suse.de> Sender: owner-linux-mm@kvack.org Return-Path: To: Andi Kleen Cc: Adam Litke , linux-mm@kvack.org, christoph@lameter.com, kenneth.w.chen@intel.com List-ID: On Wed, Aug 17, 2005 at 11:04:32PM +0200, Andi Kleen wrote: > > What about the overcommit issue Ken noted? It needs to be solved > in some way at least, either with the full check or the lazy simple > check. Hrm... I'm not 100% convinced that just allowing overcommit isn't the right thing to do. Overcommit has some unfortunate consequences, but the semantics are clearly defined and trivial to implement. 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. If we add copy-on-write for hugepages (i.e. MAP_PRIVATE support) strict accounting is even harder to implement, and has clearly-wrong behaviour in some circumstances: a process using most of the system's hugepages, mapped MAP_PRIVATE couldn't fork()/exec() a trivial helper program. > Also I still think your get_user_pages approach is questionable. > > -Andi > -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/people/dgibson -- 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