[ovs-dev] 答复: [PATCH v6] Use TPACKET_V3 to accelerate veth for userspace datapath

William Tu u9012063 at gmail.com
Sat Mar 14 14:17:48 UTC 2020


On Fri, Mar 13, 2020 at 9:45 PM Yi Yang (杨燚)-云服务集团 <yangyi01 at inspur.com> wrote:
>
> Io_uring is a feature brought in by Linux kernel 5.1, so it can't be used on Linux system with kernel version < 5.1. tpacket_v3 is only one way to avoid system call on almost all the Linux kernel versions, it is unique from this perspective. Maybe you will miss it if someone fixes kernel side issue :-)
>
> In addition, according to what Flavio said, TSO can't support VXLAN currently, but in most cloud scenarios, VXLAN is only one choice, so for such cases, TSO can be ignored.
>
> My point is we can provide one option for such use cases, once kernel side issue is fixed, all the Linux distributions can apply this fix, users can get immediate benefits without change. So maybe adding a switch userspace-use-tpacket-v3 in other-config (set to False by default) is an acceptable way to handle this.
>

The tpacket_v3 patch now shows very little performance improvement.
So there is little incentive to merge and maintain this code.
Do you know if kernel side is fixed, will tpacket_v3 have better
performance improvement?

Or another way is to study io_uring and compare its performance with tpacket_v3.

William


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