[dpdk-dev] [PATCH v3 0/5] vhost: optimize enqueue

[Jianbo Liu]

On 21 September 2016 at 17:27, Wang, Zhihong <zhihong.wang at intel.com> wrote:
>
>
>> -----Original Message-----
>> From: Jianbo Liu [mailto:jianbo.liu at linaro.org]
>> Sent: Wednesday, September 21, 2016 4:50 PM
>> To: Maxime Coquelin <maxime.coquelin at redhat.com>
>> Cc: Wang, Zhihong <zhihong.wang at intel.com>; dev at dpdk.org;
>> yuanhan.liu at linux.intel.com
>> Subject: Re: [dpdk-dev] [PATCH v3 0/5] vhost: optimize enqueue
>>
>> Hi Maxime,
>>
>> On 22 August 2016 at 16:11, Maxime Coquelin
>> <maxime.coquelin at redhat.com> wrote:
>> > Hi Zhihong,
>> >
>> > On 08/19/2016 07:43 AM, Zhihong Wang wrote:
>> >>
>> >> This patch set optimizes the vhost enqueue function.
>> >>
>> ...
>>
>> >
>> > My setup consists of one host running a guest.
>> > The guest generates as much 64bytes packets as possible using
>>
>> Have you tested with other different packet size?
>> My testing shows that performance is dropping when packet size is more
>> than 256.
>
>
> Hi Jianbo,
>
> Thanks for reporting this.
>
>  1. Are you running the vector frontend with mrg_rxbuf=off?
>
>  2. Could you please specify what CPU you're running? Is it Haswell
>     or Ivy Bridge?
>
>  3. How many percentage of drop are you seeing?
>
> This is expected by me because I've already found the root cause and
> the way to optimize it, but since it missed the v0 deadline and
> requires changes in eal/memcpy, I postpone it to the next release.
>
> After the upcoming optimization the performance for packets larger
> than 256 will be improved, and the new code will be much faster than
> the current code.
>

Sorry, I tested on an ARM server, but I wonder if there is the same
issue for x86 platform.

>> > pktgen-dpdk. The hosts forwards received packets back to the guest
>> > using testpmd on vhost pmd interface. Guest's vCPUs are pinned to
>> > physical CPUs.
>> >
>> > I tested it with and without your v1 patch, with and without
>> > rx-mergeable feature turned ON.
>> > Results are the average of 8 runs of 60 seconds:
>> >
>> > Rx-Mergeable ON : 7.72Mpps
>> > Rx-Mergeable ON + "vhost: optimize enqueue" v1: 9.19Mpps
>> > Rx-Mergeable OFF: 10.52Mpps
>> > Rx-Mergeable OFF + "vhost: optimize enqueue" v1: 10.60Mpps
>> >