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

[Avi Kivity <avi@cloudius-systems.com>]

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.