From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:49207) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UBMM9-0005lr-Ot for qemu-devel@nongnu.org; Fri, 01 Mar 2013 04:34:23 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UBMM8-0003X1-Ax for qemu-devel@nongnu.org; Fri, 01 Mar 2013 04:34:21 -0500 Received: from mail-wg0-f51.google.com ([74.125.82.51]:40596) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UBMM8-0003Wp-5G for qemu-devel@nongnu.org; Fri, 01 Mar 2013 04:34:20 -0500 Received: by mail-wg0-f51.google.com with SMTP id 8so2276903wgl.30 for ; Fri, 01 Mar 2013 01:34:19 -0800 (PST) Sender: Paolo Bonzini Message-ID: <51307618.6010708@redhat.com> Date: Fri, 01 Mar 2013 10:34:16 +0100 From: Paolo Bonzini MIME-Version: 1.0 References: <512FE6C3.5030409@linux.vnet.ibm.com> In-Reply-To: <512FE6C3.5030409@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC] parallelize migration_bitmap_sync() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael R. Hines" Cc: "qemu-devel@nongnu.org" Il 01/03/2013 00:22, Michael R. Hines ha scritto:te > Hi, > > Currently migration_bitmap_sync() is very expensive: on the order of > 15-20 milliseconds by my count using timestamps (for a simple 2GB ram > virtual machine). > Until new EPT processor versions come out in 2014, we need software > support for cutting this time down much lower........by at least an > order of magnitude. > > Would anyone be opposed to me writing a patch that creates N threads and > dividing up the migration_bitmap_sync() function to have the dirty page > scanning run in parallel? Yes, that's a possibility. You can make a quick prototype using OpenMP. But Juan is working on making the dirty bitmap really a bitmap (not a "bytemap"). That should speed up migration_bitmap_sync by a factor of 64 (i.e. sizeof(long)*8). Paolo