Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030293AbWEKP75 (ORCPT ); Thu, 11 May 2006 11:59:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030300AbWEKP75 (ORCPT ); Thu, 11 May 2006 11:59:57 -0400 Received: from e3.ny.us.ibm.com ([32.97.182.143]:57741 "EHLO e3.ny.us.ibm.com") by vger.kernel.org with ESMTP id S1030293AbWEKP75 (ORCPT ); Thu, 11 May 2006 11:59:57 -0400 Subject: Re: [RFC] Hugetlb demotion for x86 From: Adam Litke To: Hugh Dickins Cc: Christoph Hellwig , linux-mm@kvack.kernel.org, linux-kernel@vger.kernel.org In-Reply-To: References: <1147287400.24029.81.camel@localhost.localdomain> <20060510200516.GA30346@infradead.org> <1147293156.24029.95.camel@localhost.localdomain> <20060510204928.GA31315@infradead.org> <1147297535.24029.114.camel@localhost.localdomain> Content-Type: text/plain Organization: IBM Date: Thu, 11 May 2006 10:59:53 -0500 Message-Id: <1147363194.24029.128.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.4.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1476 Lines: 35 On Thu, 2006-05-11 at 16:15 +0100, Hugh Dickins wrote: > On Wed, 10 May 2006, Adam Litke wrote: > > > > Strict overcommit is there for shared mappings. When private mapping > > I presume that by "strict overcommit" you mean "strict no overcommit". > > > support was added, people agreed that full overcommit should apply to > > private mappings for the same reasons normal page overcommit is desired. > > I'm not sure how wide that agreement was. But what I wanted to say is... > > > For one: an application using lots of private huge pages should not be > > prohibited from forking if it's likely to just exec a small helper > > program. > > This is an excellent use for madvise(start, length, MADV_DONTFORK). > Though it was added mainly for RDMA issues, it's a great way for a > program with a huge commitment to exclude areas of its address space > from the fork, so making that fork much more likely to succeed. I guess it's time for me to take a step back and explain why I am doing this. libhugetlbfs (announced here recently) has the ability to remap an executable's ELF segments into huge pages. So madvise(MADV_DONTFORK) would be pretty bad ;) -- Adam Litke - (agl at us.ibm.com) IBM Linux Technology Center - 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/