linux-kernel - Re: [PATCH rdma] IB/mlx5: Optimize u64 division on 32-bit arches

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Date:   Wed, 4 Mar 2020 13:19:25 -0400
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Alexander Lobakin <alobakin@...nk.ru>
Cc:     Leon Romanovsky <leon@...nel.org>,
        Doug Ledford <dledford@...hat.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Maxim Mikityanskiy <maximmi@...lanox.com>,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH rdma] IB/mlx5: Optimize u64 division on 32-bit arches

On Mon, Feb 17, 2020 at 10:36:29AM +0300, Alexander Lobakin wrote:
> Commit f164be8c0366 ("IB/mlx5: Extend caps stage to handle VAR
> capabilities") introduced a straight "/" division of the u64
> variable "bar_size".
> This was fixed with commit 685eff513183 ("IB/mlx5: Use div64_u64
> for num_var_hw_entries calculation"). However, div64_u64() is
> redundant here as mlx5_var_table::stride_size is of type u32.
> Make the actual code way more optimized on 32-bit kernels using
> div_u64() and fix 80 chars break-through by the way.
> 
> Fixes: 685eff513183 ("IB/mlx5: Use div64_u64 for num_var_hw_entries
> calculation")
> Signed-off-by: Alexander Lobakin <alobakin@...nk.ru>
> ---
>  drivers/infiniband/hw/mlx5/main.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

Applied to for-next, thanks

Jason