Re: [PATCH] net/mlx4: Treat VFs fair when handling comm_channel_events

[Leon Romanovsky <leon@kernel.org>]

On Thu, Apr 15, 2021 at 01:43:42PM +0200, Hans Westgaard Ry wrote:
> Handling comm_channel_event in mlx4_master_comm_channel uses a double
> loop to determine which slaves have requested work. The search is
> always started at lowest slave. This leads to unfairness; lower VFs
> tends to be prioritized over higher VFs.
> 
> The patch uses find_next_bit to determine which slaves to handle.
> Fairness is implemented by always starting at the next to the last
> start.
> 
> An MPI program has been used to measure improvements. It runs 500
> ibv_reg_mr, synchronizes with all other instances and then runs 500
> ibv_dereg_mr.
> 
> The results running 500 processes, time reported is for running 500
> calls:
> 
> ibv_reg_mr:
>              Mod.   Org.
> mlx4_1    403.356ms 424.674ms
> mlx4_2    403.355ms 424.674ms
> mlx4_3    403.354ms 424.674ms
> mlx4_4    403.355ms 424.674ms
> mlx4_5    403.357ms 424.677ms
> mlx4_6    403.354ms 424.676ms
> mlx4_7    403.357ms 424.675ms
> mlx4_8    403.355ms 424.675ms
> 
> ibv_dereg_mr:
>              Mod.   Org.
> mlx4_1    116.408ms 142.818ms
> mlx4_2    116.434ms 142.793ms
> mlx4_3    116.488ms 143.247ms
> mlx4_4    116.679ms 143.230ms
> mlx4_5    112.017ms 107.204ms
> mlx4_6    112.032ms 107.516ms
> mlx4_7    112.083ms 184.195ms
> mlx4_8    115.089ms 190.618ms
> 
> Suggested-by: Håkon Bugge <haakon.bugge@oracle.com>
> Signed-off-by: Hans Westgaard Ry <hans.westgaard.ry@oracle.com>
> ---
>  drivers/net/ethernet/mellanox/mlx4/cmd.c  | 75 +++++++++++++++++--------------
>  drivers/net/ethernet/mellanox/mlx4/mlx4.h |  1 +
>  2 files changed, 43 insertions(+), 33 deletions(-)

Please fix kbuild error and resubmit to the netdev ML with Tariq CCed.

Thanks