Provide a zero-copy method on KVM virtio-net.
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From: Shirley Ma on 2 Aug 2010 12:20 Hello Michael, On Sun, 2010-08-01 at 11:31 +0300, Michael S. Tsirkin wrote: > Could you provide an example of a good setup? > Specifically, is it a good idea for the vhost thread > to inherit CPU affinities from qemu? I need to retest my set up with multi-threads vhost. My previous set up applies to single thread vhost. The single stream netperf/netserver set up, for example, if we have two quad-cores sockets to get the consistent 9.4Gb/s BW: socket 1: cpu0: netperf/netserver cpu1: ixgbe 10GbE NIC IRQ cpu2: I/O thread cpu3: vhost thread socket 2: cpu0: QEMU VCPU0 cpu1: QEMU VCPU1 cpu2: cpu3: Thanks Shirley -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Shirley Ma on 2 Aug 2010 12:30 On Mon, 2010-08-02 at 19:11 +0300, Avi Kivity wrote: > I don't understand this. gup_fast() only calls gup() if the page is > swapped out or read-only. Oh, I used the page as read-only on xmit path. Should I use write instead? Thanks Shirley -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Xin, Xiaohui on 3 Aug 2010 04:50 >-----Original Message----- >From: Shirley Ma [mailto:mashirle(a)us.ibm.com] >Sent: Friday, July 30, 2010 6:31 AM >To: Xin, Xiaohui >Cc: netdev(a)vger.kernel.org; kvm(a)vger.kernel.org; linux-kernel(a)vger.kernel.org; >mst(a)redhat.com; mingo(a)elte.hu; davem(a)davemloft.net; herbert(a)gondor.apana.org.au; >jdike(a)linux.intel.com >Subject: Re: [RFC PATCH v8 00/16] Provide a zero-copy method on KVM virtio-net. > >Hello Xiaohui, > >On Thu, 2010-07-29 at 19:14 +0800, xiaohui.xin(a)intel.com wrote: >> The idea is simple, just to pin the guest VM user space and then >> let host NIC driver has the chance to directly DMA to it. >> The patches are based on vhost-net backend driver. We add a device >> which provides proto_ops as sendmsg/recvmsg to vhost-net to >> send/recv directly to/from the NIC driver. KVM guest who use the >> vhost-net backend may bind any ethX interface in the host side to >> get copyless data transfer thru guest virtio-net frontend. > >Since vhost-net already supports macvtap/tun backends, do you think >whether it's better to implement zero copy in macvtap/tun than inducing >a new media passthrough device here? > >> Our goal is to improve the bandwidth and reduce the CPU usage. >> Exact performance data will be provided later. > >I did some vhost performance measurement over 10Gb ixgbe, and found that >in order to get consistent BW results, netperf/netserver, qemu, vhost >threads smp affinities are required. > >Looking forward to these results for small message size comparison. For >large message size 10Gb ixgbe BW already reached by doing vhost smp >affinity w/i offloading support, we will see how much CPU utilization it >can be reduced. > >Please provide latency results as well. I did some experimental on >macvtap zero copy sendmsg, what I have found that get_user_pages latency >pretty high. > May you share me with your performance results (including BW and latency)on vhost-net and how you get them(your configuration and especially with the affinity settings)? Thanks Xiaohui >Thanks >Shirley > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Shirley Ma on 3 Aug 2010 12:00 Hello Xiaohui, On Tue, 2010-08-03 at 16:48 +0800, Xin, Xiaohui wrote: > May you share me with your performance results (including BW and > latency)on > vhost-net and how you get them(your configuration and especially with > the affinity > settings)? My macvtap zero copy is incomplete, I am testing sendmsg only now. The initial performance is not good especially for latency (zero copy vs. copy). I am still working on it to find out why and how to improve. That's the reason I am eager to know your performance results and how much performance gain you have seen. Since your patch has completed. I would try your patch here for performance. If you have some performance results to share here that would be great. Thanks Shirley -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Dong, Eddie on 3 Aug 2010 22:20 Arnd Bergmann wrote: > On Friday 30 July 2010 17:51:52 Shirley Ma wrote: >> On Fri, 2010-07-30 at 16:53 +0800, Xin, Xiaohui wrote: >>>> Since vhost-net already supports macvtap/tun backends, do you think >>>> whether it's better to implement zero copy in macvtap/tun than >>>> inducing a new media passthrough device here? >>>> >>> >>> I'm not sure if there will be more duplicated code in the kernel. >> >> I think it should be less duplicated code in the kernel if we use >> macvtap to support what media passthrough driver here. Since macvtap >> has support virtio_net head and offloading already, the only missing >> func is zero copy. Also QEMU supports macvtap, we just need add a >> zero copy flag in option. > > Yes, I fully agree and that was one of the intended directions for > macvtap to start with. Thank you so much for following up on that, > I've long been planning to work on macvtap zero-copy myself but it's > now lower on my priorities, so it's good to hear that you made > progress on it, even if there are still performance issues. > But zero-copy is a Linux generic feature that can be used by other VMMs as well if the BE service drivers want to incorporate. If we can make mp device VMM-agnostic (it may be not yet in current patch), that will help Linux more. Thx, Eddie-- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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