From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57294) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Va3YX-0000fm-2i for qemu-devel@nongnu.org; Sat, 26 Oct 2013 09:05:35 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Va3YQ-0000aq-LV for qemu-devel@nongnu.org; Sat, 26 Oct 2013 09:05:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43136) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Va3YQ-0000aj-Bd for qemu-devel@nongnu.org; Sat, 26 Oct 2013 09:05:22 -0400 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r9QD5LNK032223 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Sat, 26 Oct 2013 09:05:21 -0400 Message-ID: <526BBE0E.5050500@redhat.com> Date: Sat, 26 Oct 2013 15:05:18 +0200 From: Max Reitz MIME-Version: 1.0 References: <1378106712-29856-1-git-send-email-mreitz@redhat.com> <523B134C.8060902@redhat.com> <20130920103202.GA14159@stefanha-thinkpad.redhat.com> <526BBD8D.7010301@redhat.com> In-Reply-To: <526BBD8D.7010301@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v5 0/8] Add metadata overlap checks List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: Kevin Wolf , qemu-devel@nongnu.org Am 26.10.2013 15:03, schrieb Max Reitz: > Am 20.09.2013 12:32, schrieb Stefan Hajnoczi: >> On Thu, Sep 19, 2013 at 05:07:56PM +0200, Max Reitz wrote: >>> As far as I understand, the I/O speed (the duration of an I/O >>> operation) should be pretty much the same for all scenarios, >>> however, the latency is the value in question (since the overlap >>> checks should affect the latency only). >> The other value to look at is the host CPU consumption per I/O. In >> other words, the CPU overhead added by performing the extra checks: >> >> efficiency = avg throughput / avg cpu utilization >> >> Once CPU consumption reaches 100% the workload is CPU-bound and we have >> a bottleneck. >> >> Hopefully the efficiency doesn't change noticably either, then we know >> there is no big impact from the extra checks. >> >> Stefan > Okay, after fixing the VM state in qcow2, I was now finally able to > actually perform the CPU benchmark. On second thought, it wasn't really > neccessary, since I performed most of the tests in RAM anyway, so the > CPU was already the bottleneck for these tests. I forgot to mention: I used the qemu from Kevin's current block branch for these tests. Max > I ran bonnie++ (bonnie++ -s 4g -n 0 -x 16) from an arch live CD ISO on a > 5 GB qcow2 image formatted as ext4, both residing in /tmp; I prepared > the VM state to the point where I just had to press Enter to perform the > test and shut down the VM. I then performed a snapshot and used this > image as the basis for two tests, one with no overlap checks enabled and > one with all of them enabled. > > The time output for both qemu instances was respectively: > > echo 'sendkey ret' | time $QEMU_DIR/x86_64-softmmu/qemu-system-x86_64 > -cdrom arch.iso -drive file=base.qcow2,overlap-check=none -enable-kvm > -vga std -m 512 -loadvm 0 -monitor stdio > d 294.42s user 117.72s system 98% cpu 6:58.00 total > > echo 'sendkey ret' | time $QEMU_DIR/x86_64-softmmu/qemu-system-x86_64 > -cdrom arch.iso -drive file=base.qcow2,overlap-check=all -enable-kvm > -vga std -m 512 -loadvm 0 -monitor stdio > d 298.87s user 119.55s system 100% cpu 6:56.37 total > > So, as you can see, the CPU time differs only marginally (using all > overlap checks instead of none took 1.52 % more CPU time). > > Max