Re: [dpdk-dev] [dpdk-stable] [PATCH] net/mlx5: fix number of retries for UAR allocation

[Thomas Monjalon <thomas@monjalon.net>]

05/08/2020 16:14, Thomas Monjalon:
> 03/08/2020 11:18, Dekel Peled:
> > Previous patch added definition of number of retries for UAR allocation.
> > This value is adequate for x86 systems with 4K pages.
> > On power9 system with 64K pages the required value is 32.
> > This patch updates the defined value from 2 to 32.
> 
> What about bigger pages?
> 
> > Fixes: a0bfe9d56f74 ("net/mlx5: fix UAR memory mapping type")
> > Cc: stable@dpdk.org
> 
> No need of stable@dpdk.org because it was introduced in this release.
> 
> > Signed-off-by: Dekel Peled <dekelp@mellanox.com>
> > Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
> > ---
> >  drivers/net/mlx5/mlx5_defs.h | 4 +---
> >  1 file changed, 1 insertion(+), 3 deletions(-)
> > 
> > diff --git a/drivers/net/mlx5/mlx5_defs.h b/drivers/net/mlx5/mlx5_defs.h
> > index e5f7acc..c26d5a2 100644
> > --- a/drivers/net/mlx5/mlx5_defs.h
> > +++ b/drivers/net/mlx5/mlx5_defs.h
> > @@ -202,9 +202,7 @@
> >   * UAR base address if UAR was not the first object in the UAR page.
> >   * It caused the PMD failure and we should try to get another UAR
> >   * till we get the first one with non-NULL base address returned.
> > - * Should follow the rdma_core internal (not exported) definition
> > - * MLX5_NUM_NON_FP_BFREGS_PER_UAR.
> >   */
> > -#define MLX5_ALLOC_UAR_RETRY 2
> > +#define MLX5_ALLOC_UAR_RETRY 32
> 
> It is missing a comment to explain the calculation with 64K page.

It seems getting reasons for this magic workaround is not trivial.

Applied, thanks