[PATCH net] mlxsw: spectrum_buffers: Set up a dedicated pool for BUM traffic

[PATCH net] mlxsw: spectrum_buffers: Set up a dedicated pool for BUM traffic

[Petr Machata]

MC-aware mode was recently enabled by mlxsw on Spectrum switches in
commit 7b8195306694 ("mlxsw: spectrum: Configure MC-aware mode on mlxsw
ports"). Unfortunately, testing has shown that the fix is incomplete and
in the presented form actually makes the problem even worse, because any
amount of MC traffic causes UC disruption.

The reason for this is that currently, mlxsw configures the MC-specific
TCs (8..15) to map to pool 0. It also configures a maximum buffer size
of 0, but for MC traffic that maximum is disregarded and not part of the
quota. Therefore MC traffic is always admitted to the egress buffer.

Fix the configuration by directing the MC TCs into pool 15, which is
dedicated to MC traffic and recognized as such by the silicon.

Fixes: 7b8195306694 ("mlxsw: spectrum: Configure MC-aware mode on mlxsw ports")
Signed-off-by: Petr Machata <petrm@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
---
 drivers/net/ethernet/mellanox/mlxsw/spectrum_buffers.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_buffers.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_buffers.c
index 4327487553c5..3589432d1643 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_buffers.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_buffers.c
@@ -337,14 +337,14 @@ static const struct mlxsw_sp_sb_cm mlxsw_sp_sb_cms_egress[] = {
 	MLXSW_SP_SB_CM(1500, 9, 0),
 	MLXSW_SP_SB_CM(1500, 9, 0),
 	MLXSW_SP_SB_CM(1500, 9, 0),
-	MLXSW_SP_SB_CM(0, 0, 0),
-	MLXSW_SP_SB_CM(0, 0, 0),
-	MLXSW_SP_SB_CM(0, 0, 0),
-	MLXSW_SP_SB_CM(0, 0, 0),
-	MLXSW_SP_SB_CM(0, 0, 0),
-	MLXSW_SP_SB_CM(0, 0, 0),
-	MLXSW_SP_SB_CM(0, 0, 0),
-	MLXSW_SP_SB_CM(0, 0, 0),
+	MLXSW_SP_SB_CM(0, 140000, 15),
+	MLXSW_SP_SB_CM(0, 140000, 15),
+	MLXSW_SP_SB_CM(0, 140000, 15),
+	MLXSW_SP_SB_CM(0, 140000, 15),
+	MLXSW_SP_SB_CM(0, 140000, 15),
+	MLXSW_SP_SB_CM(0, 140000, 15),
+	MLXSW_SP_SB_CM(0, 140000, 15),
+	MLXSW_SP_SB_CM(0, 140000, 15),
 	MLXSW_SP_SB_CM(1, 0xff, 0),
 };
 
-- 
2.4.11

Re: [PATCH net] mlxsw: spectrum_buffers: Set up a dedicated pool for BUM traffic

[David Miller]

From: Petr Machata <petrm@mellanox.com>
Date: Wed, 05 Sep 2018 12:16:00 +0200

> MC-aware mode was recently enabled by mlxsw on Spectrum switches in
> commit 7b8195306694 ("mlxsw: spectrum: Configure MC-aware mode on mlxsw
> ports"). Unfortunately, testing has shown that the fix is incomplete and
> in the presented form actually makes the problem even worse, because any
> amount of MC traffic causes UC disruption.
> 
> The reason for this is that currently, mlxsw configures the MC-specific
> TCs (8..15) to map to pool 0. It also configures a maximum buffer size
> of 0, but for MC traffic that maximum is disregarded and not part of the
> quota. Therefore MC traffic is always admitted to the egress buffer.
> 
> Fix the configuration by directing the MC TCs into pool 15, which is
> dedicated to MC traffic and recognized as such by the silicon.
> 
> Fixes: 7b8195306694 ("mlxsw: spectrum: Configure MC-aware mode on mlxsw ports")
> Signed-off-by: Petr Machata <petrm@mellanox.com>
> Acked-by: Jiri Pirko <jiri@mellanox.com>

Applied, thank you.