Re: [dpdk-dev] [PATCH v6 1/2] mbuf: provide rte_pktmbuf_alloc_bulk API

[Olivier MATZ <olivier.matz@6wind.com>]

On 02/26/2016 08:39 AM, Xie, Huawei wrote:
>>>> With 8 mbufs allocated, there is about 6% performance increase using inline.
>>>> With 16 mbufs allocated, we could still observe obvious performance
>>>> difference, though only 1%-2%
> 

> On 2/24/2016 9:23 PM, Ananyev, Konstantin wrote:
>> As you can see right now we have all mbuf alloc/free routines as static inline.
>> And I think we would like to keep it like that.
>> So why that particular function should be different?
>> After all that function is nothing more than a wrapper 
>> around rte_mempool_get_bulk()  unrolled by 4 loop {rte_pktmbuf_reset()}
>> So unless mempool get/put API would change, I can hardly see there could be any ABI
>> breakages in future. 
>> About 'real world' performance gain - it was a 'real world' performance problem,
>> that we tried to solve by introducing that function:
>> http://dpdk.org/ml/archives/dev/2015-May/017633.html
>>
>> And according to the user feedback, it does help:  
>> http://dpdk.org/ml/archives/dev/2016-February/033203.html

For me, there's no doubt this function will help in real world use
cases. That's also true that today most (oh no, all) datapath mbuf
functions are inline. Although I understand Panu's point of view
about the use of inline functions, trying to de-inline some functions
of the mbuf API (and others APIs like mempool or ring) would require
a deep analysis first to check the performance impact. And I think there
would be an impact for most of them.

In this particular case, as the function does bulk allocations, it
probably tempers the cost of the function call, and that's why I
was curious of any comparison with/without inlining. But I'm not
sure having this only function as non-inline makes a lot of sense.

So:
Acked-by: Olivier Matz <olivier.matz@6wind.com>