Re: [PATCH v1 00/15] io_uring zero copy rx

David Wei
2024-10-11T00:35:50Z

On 2024-10-09 11:21, Pedro Tammela wrote:
> On 09/10/2024 13:55, Mina Almasry wrote:
>> [...]
>>
>> If not, I would like to see a comparison between TCP RX zerocopy and
>> this new io-uring zerocopy. For Google for example we use the TCP RX
>> zerocopy, I would like to see perf numbers possibly motivating us to
>> move to this new thing.
>>
>> [1] https://lwn.net/Articles/752046/
>>
>
> Hi!
>
> From my own testing, the TCP RX Zerocopy is quite heavy on the page unmapping side. Since the io_uring implementation is expected to be lighter (see patch 11), I would expect a simple comparison to show better numbers for io_uring.

Hi Pedro, I will add TCP_ZEROCOPY_RECEIVE to kperf and compare in the
next patchset.

>
> To be fair to the existing implementation, it would then be needed to be paired with some 'real' computation, but that varies a lot. As we presented in netdevconf this year, HW-GRO eventually was the best option for us (no app changes, etc...) but still a case by case decision.

Why is there a need to add some computation to the benchmarks? A
benchmark is meant to be just that - a simple comparison that just looks
at the overheads of the stack. Real workloads are complex, I don't see
this feature as a universal win in all cases, but very workload and
userspace architecture dependent.

As for HW-GRO, whynotboth.jpg?