From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id ABF636B0044 for ; Tue, 27 Oct 2009 16:25:39 -0400 (EDT) Date: Tue, 27 Oct 2009 13:25:33 -0700 From: Chris Wright Subject: Re: RFC: Transparent Hugepage support Message-ID: <20091027202533.GB2726@sequoia.sous-sol.org> References: <20091026185130.GC4868@random.random> <20091027182109.GA5753@random.random> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091027182109.GA5753@random.random> Sender: owner-linux-mm@kvack.org To: Andrea Arcangeli Cc: Christoph Lameter , linux-mm@kvack.org, Marcelo Tosatti , Adam Litke , Avi Kivity , Izik Eidus , Hugh Dickins , Nick Piggin , Andrew Morton List-ID: * Andrea Arcangeli (aarcange@redhat.com) wrote: > On Tue, Oct 27, 2009 at 04:42:39PM -0400, Christoph Lameter wrote: > > > 1) hugepages have to be swappable or the guest physical memory remains > > > locked in RAM and can't be paged out to swap > > > > Thats not such a big issue IMHO. Paging is not necessary. Swapping is > > deadly to many performance based loads. You would abort a job anyways that > > Yes, swapping is deadly to performance based loads and it should be > avoided as much as possible, but it's not nice when in order to get a > boost in guest performance when the host isn't low on memory, you lose > the ability to swap when the host is low on memory and all VM are > locked in memory like in inferior-design virtual machines that won't > ever support paging. When system starts swapping the manager can > migrate the VM to other hosts with more memory free to restore the > full RAM performance as soon as possible. Overcommit can be very > useful at maxing out RAM utilization, just like it happens for regular > linux tasks (few people runs with overcommit = 2 for this very > reason.. besides overcommit = 2 includes swap in its equation so you > can still max out ram by adding more free swap). It's also needed if something like glibc were to take advantage of it in a generic manner. thanks, -chris -- 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