Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758359Ab1EZSVu (ORCPT ); Thu, 26 May 2011 14:21:50 -0400 Received: from mx1.redhat.com ([209.132.183.28]:19591 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758298Ab1EZSVt (ORCPT ); Thu, 26 May 2011 14:21:49 -0400 Message-ID: <4DDE99F6.4030804@redhat.com> Date: Thu, 26 May 2011 21:20:38 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc15 Thunderbird/3.1.10 MIME-Version: 1.0 To: Ingo Molnar CC: James Morris , Linus Torvalds , Kees Cook , Thomas Gleixner , Peter Zijlstra , Will Drewry , Steven Rostedt , linux-kernel@vger.kernel.org, gnatapov@redhat.com, Chris Wright , Pekka Enberg Subject: Re: [PATCH 3/5] v2 seccomp_filters: Enable ftrace-based system call filtering References: <20110525180100.GY19633@outflux.net> <20110526082451.GB26775@elte.hu> <4DDE1419.3000708@redhat.com> <20110526093040.GB19536@elte.hu> <4DDE31D6.4070209@redhat.com> <20110526113842.GA27618@elte.hu> <4DDE96B7.8030006@redhat.com> <20110526181554.GB3572@elte.hu> In-Reply-To: <20110526181554.GB3572@elte.hu> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2410 Lines: 56 On 05/26/2011 09:15 PM, Ingo Molnar wrote: > * Avi Kivity wrote: > > > On 05/26/2011 02:38 PM, Ingo Molnar wrote: > > >* Avi Kivity wrote: > > > > > >> > The biggest amount of RAM is the guest RAM image - but if that is > > >> > mmap(SHARED) and mapped using hugepages then the pte overhead > > >> > from a process model is largely mitigated. > > >> > > >> That doesn't work with memory hotplug. > > > > > > Why not, if we do the sensible thing and restrict the size > > > granularity and alignment of plugged/unplugged memory regions to > > > 2MB? > > > > Once forked, you cannot have new shared anonymous memory, can you? > > We can have named shared memory. But then the benefit of transparent huge pages goes away. Of course, if some is working on extending transparent hugepages, the problem is solved. I know there is interest in this. > Incidentally i suggested this to Pekka just yesterday: i think we > should consider guest RAM images to be named files on the local > filesystem (prefixed with the disk image's name or so, for easy > identification), this will help with debugging and with swapping as > well. (This way guest RAM wont eat up regular anonymous swap space - > it will be swapped to the filesystem.) Qemu supports this via -mem-path. The motivation was supporting hugetlbfs, before THP. I can't say it was useful for debugging (but then qemu has a built in memory inspector and debugger, and supports attaching gdb to the guest). > As a sidenote, live migration might also become possible this way: in > theory we could freeze a guest to its RAM image - which can then be > copied (together with the disk image) to another box as files and > restarted there, with some some hw configuration state dumped to a > header portion of that RAM image as well. (outside of the RAM area) Live migration involves the guest running in parallel with its memory being copied over. Even a 1GB guest will take 10s over 1GbE; any reasonably sized guest will take forever. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain. -- 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/