From mboxrd@z Thu Jan 1 00:00:00 1970 From: Evgeniy Polyakov Subject: Re: QEMU PIC indirection patch for in-kernel APIC work Date: Tue, 10 Apr 2007 15:50:37 +0400 Message-ID: <20070410115035.GA2247@2ka.mipt.ru> References: <1175821357.12230.642.camel@localhost.localdomain> <46187F4E.1080807@qumranet.com> <1176087018.11664.65.camel@localhost.localdomain> <4619E6DC.3010804@qumranet.com> <1176111984.11664.90.camel@localhost.localdomain> <461A41CA.9080201@qumranet.com> <20070410080729.GB16621@2ka.mipt.ru> <461B48A8.1060904@qumranet.com> <20070410085825.GA20004@2ka.mipt.ru> <461B7334.8090807@qumranet.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, netdev To: Avi Kivity Return-path: Content-Disposition: inline In-Reply-To: <461B7334.8090807-atKUWr5tajBWk0Htik3J/w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: netdev.vger.kernel.org On Tue, Apr 10, 2007 at 02:21:24PM +0300, Avi Kivity (avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org) wrote: > >You want to implement zero-copy network device between host and guest, if > >I understood this thread correctly? > >So, for sending part, device allocates pages from receiver's memory (or > >from shared memory), receiver gets an 'interrupt' and got pages from own > >memory, which are attached to new skb and transferred up to the network > >stack. > >It can be extended to use shared ring of pages. > > > > This is what Xen does. It is actually less performant than copying, IIRC. > > The problem with flipping pages around is that physical addresses are > cached both in the kvm mmu and in the on-chip tlbs, necessitating > expensive page table walks and tlb invalidation IPIs. Hmm, I'm not familiar with Xen driver, but similar technique was used with zero-copy network sniffer some time ago, substituting userspace pages with pages containing skb data was about 25-50% faster than copying 1500 bytes in general, and in order of 10 times faster in some cases. Check a link please in case we are talking about different ideas: http://marc.info/?l=linux-netdev&m=112262743505711&w=2 -- Evgeniy Polyakov ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV