From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1NrAm5-0002TG-IG for qemu-devel@nongnu.org; Mon, 15 Mar 2010 09:56:05 -0400 Received: from [199.232.76.173] (port=57863 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NrAm5-0002Sx-6X for qemu-devel@nongnu.org; Mon, 15 Mar 2010 09:56:05 -0400 Received: from Debian-exim by monty-python.gnu.org with spam-scanned (Exim 4.60) (envelope-from ) id 1NrAm3-0005g0-Di for qemu-devel@nongnu.org; Mon, 15 Mar 2010 09:56:04 -0400 Received: from mail-pv0-f173.google.com ([74.125.83.173]:53713) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1NrAm3-0005fw-42 for qemu-devel@nongnu.org; Mon, 15 Mar 2010 09:56:03 -0400 Received: by pvf33 with SMTP id 33so1305390pvf.4 for ; Mon, 15 Mar 2010 06:56:01 -0700 (PDT) Message-ID: <4B9E3C6D.7050002@codemonkey.ws> Date: Mon, 15 Mar 2010 08:55:57 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] Ideas wiki for GSoC 2010 References: <20100310183023.6632aece@redhat.com> <4B9E2745.7060903@redhat.com> <20100315125313.GK9457@il.ibm.com> <20100315130310.GE13108@8bytes.org> <4B9E320E.7040605@redhat.com> <20100315132448.GF13108@8bytes.org> In-Reply-To: <20100315132448.GF13108@8bytes.org> 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: Joerg Roedel Cc: Muli Ben-Yehuda , agraf@suse.de, aliguori@us.ibm.com, kvm@vger.kernel.org, jan.kiszka@siemens.com, qemu-devel@nongnu.org, Luiz Capitulino , Avi Kivity , agl@us.ibm.com, Nadav Amit , Ben-Ami Yassour1 On 03/15/2010 08:24 AM, Joerg Roedel wrote: > On Mon, Mar 15, 2010 at 03:11:42PM +0200, Avi Kivity wrote: > >> On 03/15/2010 03:03 PM, Joerg Roedel wrote: >> >>> >>>>> I will add another project - iommu emulation. Could be very useful >>>>> for doing device assignment to nested guests, which could make >>>>> testing a lot easier. >>>>> >>>>> >>>> Our experiments show that nested device assignment is pretty much >>>> required for I/O performance in nested scenarios. >>>> >>>> >>> Really? I did a small test with virtio-blk in a nested guest (disk read >>> with dd, so not a real benchmark) and got a reasonable read-performance >>> of around 25MB/s from the disk in the l2-guest. >>> >>> >>> >> Your guest wasn't doing a zillion VMREADs and VMWRITEs every exit. >> >> I plan to reduce VMREAD/VMWRITE overhead for kvm, but not much we can do >> for other guests. >> > Does it matter for the ept-on-ept case? The initial patchset of > nested-vmx implemented it and they reported a performance drop of around > 12% between levels which is reasonable. So I expected the loss of > io-performance for l2 also reasonable in this case. My small measurement > was also done using npt-on-npt. > But that was something like kernbench IIRC which is actually exit light once ept is enabled. Network IO is typically exit heavy and becomes something more of a pathological work load (both for nested ept and nested npt). Regards, Anthony Liguori > Joerg > > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >