From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=45071 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OGwo5-00040q-5Z for qemu-devel@nongnu.org; Tue, 25 May 2010 12:16:43 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OGwo3-0003Im-ED for qemu-devel@nongnu.org; Tue, 25 May 2010 12:16:41 -0400 Received: from mx1.redhat.com ([209.132.183.28]:6057) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OGwo3-0003IS-7E for qemu-devel@nongnu.org; Tue, 25 May 2010 12:16:39 -0400 Message-ID: <4BFBF7D4.80900@redhat.com> Date: Tue, 25 May 2010 19:16:20 +0300 From: Avi Kivity MIME-Version: 1.0 Subject: Re: [Qemu-devel] [RFC PATCH 1/1] ceph/rbd block driver for qemu-kvm References: <20100519192222.GD61706@ncolin.muc.de> <4BF5A9D2.5080609@codemonkey.ws> <4BF91937.2070801@redhat.com> <4BFBAE46.5050801@redhat.com> <4BFBB3C1.9020905@redhat.com> <4BFBCFAC.9070807@codemonkey.ws> <4BFBD13C.60605@redhat.com> <4BFBD20E.5060207@codemonkey.ws> <4BFBD2D5.2000201@redhat.com> <4BFBD6CD.3000503@codemonkey.ws> <4BFBD82F.3020404@redhat.com> <4BFBD943.8020704@codemonkey.ws> <4BFBE614.9080306@redhat.com> <4BFBE64F.6020901@codemonkey.ws> In-Reply-To: <4BFBE64F.6020901@codemonkey.ws> 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: Anthony Liguori Cc: Kevin Wolf , kvm@vger.kernel.org, qemu-devel@nongnu.org, Blue Swirl , ceph-devel@vger.kernel.org, Christian Brunner On 05/25/2010 06:01 PM, Anthony Liguori wrote: > On 05/25/2010 10:00 AM, Avi Kivity wrote: >> The latter. Why is it less important? If you don't inherit the >> memory, you can't access it. >> >>> You can also pass /dev/shm fd's via SCM_RIGHTs to establish shared >>> memory segments dynamically. >> >> Doesn't work for anonymous memory. > > What's wrong with /dev/shm memory? The kernel treats anonymous and nonymous memory differently for swapping (see /proc/sys/vm/swappiness); transparent hugepages won't work for /dev/shm (though it may be argued that that's a problem with thp); setup (/dev/shm defaults to half memory IIRC, we want mem+swap); different cgroup handling; somewhat clunky (a minor concern to be sure). Nothing is a killer, but we should prefer anonymous memory. -- error compiling committee.c: too many arguments to function