From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53749) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y0uYD-0002nn-ST for qemu-devel@nongnu.org; Tue, 16 Dec 2014 11:00:50 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Y0uY4-0005k9-FU for qemu-devel@nongnu.org; Tue, 16 Dec 2014 11:00:41 -0500 Received: from mx-v6.kamp.de ([2a02:248:0:51::16]:47612 helo=mx01.kamp.de) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y0uY4-0005jt-5R for qemu-devel@nongnu.org; Tue, 16 Dec 2014 11:00:32 -0500 Message-ID: <5490571B.8070207@kamp.de> Date: Tue, 16 Dec 2014 17:00:27 +0100 From: Peter Lieven MIME-Version: 1.0 References: <1418743287-20467-1-git-send-email-pl@kamp.de> <20141216154832.GB3301@noname.str.redhat.com> In-Reply-To: <20141216154832.GB3301@noname.str.redhat.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH V2 0/4] *virtio-blk: add multiread support List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: famz@redhat.com, benoit@irqsave.net, ming.lei@canonical.com, armbru@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com, pbonzini@redhat.com, mreitz@redhat.com On 16.12.2014 16:48, Kevin Wolf wrote: > Am 16.12.2014 um 16:21 hat Peter Lieven geschrieben: >> this series adds the long missing multiread support to virtio-blk. >> >> some remarks: >> - i introduced rd_merged and wr_merged block accounting stats to >> blockstats as a generic interface which can be set from any >> driver that will introduce multirequest merging in the future. >> - the knob to disable request merging is not yet there. I would >> add it to the device properties also as a generic interface >> to have the same switch for any driver that might introduce >> request merging in the future. As there has been no knob in >> the past I would post this as a seperate series as it needs >> some mangling in parameter parsing which might lead to further >> discussions. >> - the old multiwrite interface is still there and might be removed. >> >> v1->v2: >> - add overflow checking for nb_sectors [Kevin] >> - do not change the name of the macro of max mergable requests. [Fam] > Diff to v1 looks good. Now I just need to check what it does to the > performance. Did you run any benchmarks yourself? I ran several installs of Debian/Ubuntu, Booting of Windows and Linux systems. I looked at rd_total_time_ns and wr_total_time_ns and saw no increase. Ofter I even saw even a decrease. {rd,wr}_total_time_ns measures the time from virtio_blk_handle_request to virtio_blk_rw_complete. So it seems to be a good indicator for the time spent with I/O. What you could to is post it on the top of your fio testing stack and look at the throughput. Sequential Reads should be faster. The rest not worse. Peter