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

Jianbo Liu jianbo.liu at linaro.org
Thu Sep 22 07:47:45 CEST 2016


On 22 September 2016 at 10:29, Yuanhan Liu <yuanhan.liu at linux.intel.com> wrote:
> On Wed, Sep 21, 2016 at 08:54:11PM +0800, Jianbo Liu wrote:
>> >> > 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?
>> >
Yes, my testing is mrg_rxbuf=off, but not vector frontend PMD.

>> >  2. Could you please specify what CPU you're running? Is it Haswell
>> >     or Ivy Bridge?
>> >
It's an ARM server.

>> >  3. How many percentage of drop are you seeing?
The testing result:
size (bytes)     improvement (%)
64                   3.92
128                 11.51
256                  24.16
512                  -13.79
1024                -22.51
1500                -12.22
A correction is that performance is dropping if byte size is larger than 512.

>> >
>> > 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.
>
> Would you please provide more details? Say, answer the two left
> questions from Zhihong?
>
> Thanks.
>
>         --yliu


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