[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH net-next] xen-netfront: convert to GRO API and advertise this feature
On Sep 22, 2013, at 5:09 AM, Wei Liu <wei.liu2@xxxxxxxxxx> wrote: > On Sun, Sep 22, 2013 at 02:29:15PM +0800, Jason Wang wrote: >> On 09/22/2013 12:05 AM, Wei Liu wrote: >>> Anirban was seeing netfront received MTU size packets, which downgraded >>> throughput. The following patch makes netfront use GRO API which >>> improves throughput for that case. >>> >>> Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx> >>> Signed-off-by: Anirban Chakraborty <abchak@xxxxxxxxxxx> >>> Cc: Ian Campbell <ian.campbell@xxxxxxxxxx> >> >> Maybe a dumb question: doesn't Xen depends on the driver of host card to >> do GRO and pass it to netfront? What the case that netfront can receive > > The would be the ideal situation. Netback pushes large packets to > netfront and netfront sees large packets. > >> a MTU size packet, for a card that does not support GRO in host? Doing > > However Anirban saw the case when backend interface receives large > packets but netfront sees MTU size packets, so my thought is there is > certain configuration that leads to this issue. As we cannot tell > users what to enable and what not to enable so I would like to solve > this within our driver. > >> GRO twice may introduce extra overheads. >> > > AIUI if the packet that frontend sees is large already then the GRO path > is quite short which will not introduce heavy penalty, while on the > other hand if packet is segmented doing GRO improves throughput. > Thanks Wei, for explaining and submitting the patch. I would like add following to what you have already mentioned. In my configuration, I was seeing netback was pushing large packets to the guest (Centos 6.4) but the netfront was receiving MTU sized packets. With this patch on, I do see large packets received on the guest interface. As a result there was substantial throughput improvement in the guest side (2.8 Gbps to 3.8 Gbps). Also, note that the host NIC driver was enabled for GRO already. -Anirban _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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