Re: [PATCH net-next] selftests: net/forwarding: spawn sh inside vrf to speed up ping loop

[Ido Schimmel <idosch@nvidia.com>]

On Sat, Aug 17, 2024 at 01:36:59PM -0700, Jakub Kicinski wrote:
> Looking at timestamped output of netdev CI reveals that
> most of the time in forwarding tests for custom route
> hashing is spent on a single case, namely the test which
> uses ping (mausezahn does not support flow labels).
> 
> On a non-debug kernel we spend 714 of 730 total test
> runtime (97%) on this test case. While having flow label
> support in a traffic gen tool / mausezahn would be best,
> we can significantly speed up the loop by putting ip vrf exec
> outside of the iteration.
> 
> In a test of 1000 pings using a normal loop takes 50 seconds
> to finish. While using:
> 
>   ip vrf exec $vrf sh -c "$loop-body"
> 
> takes 12 seconds (1/4 of the time).
> 
> Some of the slowness is likely due to our inefficient virtualization
> setup, but even on my laptop running "ip link help" 16k times takes
> 25-30 seconds, so I think it's worth optimizing even for fastest
> setups.
> 
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Tested-by: Ido Schimmel <idosch@nvidia.com>

Thanks!