Re: [dpdk-dev] VMXNET3 on vmware, ping delay

[Thomas Monjalon <thomas.monjalon@6wind.com>]

2015-06-25 18:46, Avi Kivity:
> On 06/25/2015 06:18 PM, Matthew Hall wrote:
> > On Thu, Jun 25, 2015 at 09:14:53AM +0000, Vass, Sandor (Nokia - HU/Budapest) wrote:
> >> According to my understanding each packet should go
> >> through BR as fast as possible, but it seems that the rte_eth_rx_burst
> >> retrieves packets only when there are at least 2 packets on the RX queue of
> >> the NIC. At least most of the times as there are cases (rarely - according
> >> to my console log) when it can retrieve 1 packet also and sometimes only 3
> >> packets can be retrieved...
> > By default DPDK is optimized for throughput not latency. Try a test with
> > heavier traffic.
> >
> > There is also some work going on now for DPDK interrupt-driven mode, which
> > will work more like traditional Ethernet drivers instead of polling mode
> > Ethernet drivers.
> >
> > Though I'm not an expert on it, there is also a series of ways to optimize for
> > latency, which hopefully some others could discuss... or maybe search the
> > archives / web site / Intel tuning documentation.
> >
> 
> What would be useful is a runtime switch between polling and interrupt 
> modes.  This was if the load is load you use interrupts, and as 
> mitigation, you switch to poll mode, until the load drops again.

DPDK is not a stack. It's up to the DPDK application to poll or use interrupts
when needed.