From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:37294) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UIboJ-0000ZC-2H for qemu-devel@nongnu.org; Thu, 21 Mar 2013 05:29:25 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UIboH-0004b0-IK for qemu-devel@nongnu.org; Thu, 21 Mar 2013 05:29:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33746) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UIboH-0004Zh-A3 for qemu-devel@nongnu.org; Thu, 21 Mar 2013 05:29:21 -0400 Message-ID: <514AD2EC.40700@redhat.com> Date: Thu, 21 Mar 2013 10:29:16 +0100 From: Paolo Bonzini MIME-Version: 1.0 References: <1363856971-4601-1-git-send-email-owasserm@redhat.com> In-Reply-To: <1363856971-4601-1-git-send-email-owasserm@redhat.com> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC 00/12] Migration: Remove copying of guest ram pages List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Orit Wasserman Cc: mst@redhat.com, chegu_vinod@hp.com, qemu-devel@nongnu.org, quintela@redhat.com Il 21/03/2013 10:09, Orit Wasserman ha scritto: > In migration all data is copied to a static buffer in QEMUFile, > this hurts our network bandwidth and CPU usage especially with large guests. > We switched to iovec for storing different buffers to send (even a byte field is > considered as a buffer) and use writev to send the iovec. > writev was chosen (as apposed to sendmsg) because it supprts non socket fds. > > Guest memory pages are not copied by calling a new function > qemu_put_buffer_no_copy. > The page header data and device state data are still copied into the static > buffer. This data consists of a lot of bytes and integer fields and the static > buffer is used to store it during batching. > Another improvement is changing qemu_putbe64/32/16 to create a single > buffer instead of several byte sized buffer. Very nice! I just disagree on making writev_buffer mandatory; instead, a QemuFileOps could choose between implementing either put_buffer or writev_buffer. This removes the duplicate code you have between iov_writev and block_writev_buffer. Thanks, Paolo > Orit Wasserman (12): > Add iov_writev to use writev to send iovec (also for files) > Add QemuFileWritevBuffer QemuFileOps > Add socket_writev_buffer function > Add stdio_writev_buffer function > Add block_writev_buffer function > Update bytes_xfer in qemu_put_byte > Store the data to send also in iovec > Use writev ops instead of put_buffer ops > More optimized qemu_put_be64/32/16 > Add qemu_put_buffer_no_copy > Use qemu_put_buffer_no_copy for guest memory pages > Bye Bye put_buffer > > arch_init.c | 2 +- > include/migration/qemu-file.h | 20 ++++--- > include/qemu/iov.h | 12 ++++ > savevm.c | 130 +++++++++++++++++++++++++----------------- > util/iov.c | 36 ++++++++++++ > 5 files changed, 139 insertions(+), 61 deletions(-) >