Messages in this thread |  | | Date | Mon, 16 Dec 2013 16:13:44 +0000 | From | Zoltan Kiss <> | Subject | Re: [Xen-devel] [PATCH net-next v2 0/9] xen-netback: TX grant mapping with SKBTX_DEV_ZEROCOPY instead of copy |
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On 16/12/13 06:32, annie li wrote: > > On 2013/12/13 7:48, Zoltan Kiss wrote: >> A long known problem of the upstream netback implementation that on >> the TX >> path (from guest to Dom0) it copies the whole packet from guest memory >> into >> Dom0. That simply became a bottleneck with 10Gb NICs, and generally >> it's a >> huge perfomance penalty. The classic kernel version of netback used grant >> mapping, and to get notified when the page can be unmapped, it used page >> destructors. Unfortunately that destructor is not an upstreamable >> solution. >> Ian Campbell's skb fragment destructor patch series [1] tried to solve >> this >> problem, however it seems to be very invasive on the network stack's >> code, >> and therefore haven't progressed very well. >> This patch series use SKBTX_DEV_ZEROCOPY flags to tell the stack it >> needs to >> know when the skb is freed up. That is the way KVM solved the same >> problem, >> and based on my initial tests it can do the same for us. Avoiding the >> extra >> copy boosted up TX throughput from 6.8 Gbps to 7.9 (I used a slower >> Interlagos box, both Dom0 and guest on upstream kernel, on the same >> NUMA node, >> running iperf 2.0.5, and the remote end was a bare metal box on the >> same 10Gb >> switch) > Sounds good. > Is the TX throughput gotten between one vm and one bare metal box? or > between multiple vms and bare metal? Do you have any test results with > netperf? One VM and a bare metal box. I've used only iperf.
Regards,
Zoli
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