netdev - Re: [PATCH net 7/7] mlxsw: spectrum_buffers: Add a multicast pool for Spectrum-2

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Date:   Wed, 10 Apr 2019 15:40:47 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Ido Schimmel <idosch@...lanox.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Jiri Pirko <jiri@...lanox.com>, mlxsw <mlxsw@...lanox.com>
Subject: Re: [PATCH net 7/7] mlxsw: spectrum_buffers: Add a multicast pool
 for Spectrum-2

Wed, Apr 10, 2019 at 08:58:17AM CEST, idosch@...lanox.com wrote:
>In Spectrum-1, when a multicast packet is admitted to the shared buffer
>it increases the quotas of all the ports and {port, TC} to which it is
>forwarded to.
>
>The above means that multicast packets are accounted multiple times in
>the shared buffer and can therefore cause the associated shared buffer
>pool to fill up very quickly.
>
>To work around this issue, commit e83c045e53d7 ("mlxsw:
>spectrum_buffers: Configure MC pool") added a dedicated multicast pool
>in which multicast packets are accounted.
>
>The issue is not present in Spectrum-2, but in order to be backward
>compatible with Spectrum-1, its default behavior is to allow a multicast
>packet to increase multiple egress quotas instead of one.
>
>Until the new (non-backward compatible) mode is supported, configure a
>dedicated multicast pool as in Spectrum-1.
>
>Fixes: fe099bf682ab ("mlxsw: spectrum_buffers: Add Spectrum-2 shared buffer configuration")
>Signed-off-by: Ido Schimmel <idosch@...lanox.com>
>Reviewed-by: Petr Machata <petrm@...lanox.com>

Acked-by: Jiri Pirko <jiri@...lanox.com>