From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [Qemu-devel] Ideas wiki for GSoC 2010 Date: Mon, 15 Mar 2010 08:55:57 -0500 Message-ID: <4B9E3C6D.7050002@codemonkey.ws> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Avi Kivity , Muli Ben-Yehuda , Luiz Capitulino , qemu-devel@nongnu.org, aliguori@us.ibm.com, kvm@vger.kernel.org, jan.kiszka@siemens.com, agraf@suse.de, agl@us.ibm.com, Nadav Amit , Ben-Ami Yassour1 To: Joerg Roedel Return-path: Received: from mail-px0-f181.google.com ([209.85.216.181]:41299 "EHLO mail-px0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936404Ab0CON4C (ORCPT ); Mon, 15 Mar 2010 09:56:02 -0400 Received: by pxi11 with SMTP id 11so1682169pxi.16 for ; Mon, 15 Mar 2010 06:56:01 -0700 (PDT) In-Reply-To: <20100315132448.GF13108@8bytes.org> Sender: kvm-owner@vger.kernel.org List-ID: 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 >