From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=56229 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PaZge-0003TZ-RU for qemu-devel@nongnu.org; Wed, 05 Jan 2011 15:10:25 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PaZgd-0002TI-Dq for qemu-devel@nongnu.org; Wed, 05 Jan 2011 15:10:24 -0500 Received: from e3.ny.us.ibm.com ([32.97.182.143]:47191) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PaZgd-0002SQ-96 for qemu-devel@nongnu.org; Wed, 05 Jan 2011 15:10:23 -0500 Received: from d01dlp02.pok.ibm.com (d01dlp02.pok.ibm.com [9.56.224.85]) by e3.ny.us.ibm.com (8.14.4/8.13.1) with ESMTP id p05JpX09015384 for ; Wed, 5 Jan 2011 14:51:34 -0500 Received: from d01relay01.pok.ibm.com (d01relay01.pok.ibm.com [9.56.227.233]) by d01dlp02.pok.ibm.com (Postfix) with ESMTP id 067C04DE8042 for ; Wed, 5 Jan 2011 15:07:24 -0500 (EST) Received: from d01av03.pok.ibm.com (d01av03.pok.ibm.com [9.56.224.217]) by d01relay01.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p05KADeg398040 for ; Wed, 5 Jan 2011 15:10:13 -0500 Received: from d01av03.pok.ibm.com (loopback [127.0.0.1]) by d01av03.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p05KACbc022271 for ; Wed, 5 Jan 2011 18:10:13 -0200 Message-ID: <4D24D020.2010705@linux.vnet.ibm.com> Date: Wed, 05 Jan 2011 14:10:08 -0600 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH] add MADV_DONTFORK to guest physical memory References: <20100915170824.GL5981@random.random> <20110105151012.GC15823@random.random> <4D24B22C.4010302@linux.vnet.ibm.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexander Graf Cc: Andrea Arcangeli , Anthony Liguori , "qemu-devel@nongnu.org Developers" , Michael Roth , Blue Swirl , =?ISO-8859-1?Q?Andreas_F=E4rber?= On 01/05/2011 01:44 PM, Alexander Graf wrote: > On 05.01.2011, at 19:02, Michael Roth wrote: > > >> On 01/05/2011 09:10 AM, Andrea Arcangeli wrote: >> >>> The bug is still there so I rediffed the old patch against current >>> code. >>> >>> On a related topic: could somebody give me advice on how to implement >>> a command line (command line seems enough, the other option would be >>> monitor command) to make the MADV_MERGEABLE conditional? I got KSM on >>> THP working fine but KSM may decrease performance by increasing the >>> number of copy on write and by splitting hugepages, so we'd like to be >>> able to turn off KSM on a per-VM basis (not on the whole host, which >>> of course we already can by setting /sys/kernel/mm/ksm/run to 0) so >>> that high perf VMs will keep running at maximum speed with KSM off but >>> others may still benefit from KSM. For that I need to make the below >>> MADV_MERGEABLE madvise conditional to something and the code itself >>> will be trivial, we've just to converge on a command line option >>> (hopefully quickly ;). >>> >> There was a -mem_prealloc option added a while back to set MAP_POPULATE on memory mapped in via the -mem-path option. So an analogous -mem_nomerge option or something along that line seems reasonable for conditionally unsetting QEMU_MADV_MERGEABLE. >> >> And for consistency you should probably make both your proposed changes for -mem-path'd memory as well. >> > Why not clean up all that mess and introduce a new -mem option that would just take all of the several options as parameters? > > -mem size=512,populate=on,ksm=off > > and default -m to something reasonable with the new syntax. > Yeah, that does make sense. Maybe we should consider folding it in with the -numa option too? Regards, Anthony Liguori > > Alex > >