netdev - Re: [PATCH net-next 0/5] mlxsw: Control the order of blocks in ACL region

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Message-ID: <ZR1ZNPgcbRBa8uer@kernel.org>
Date: Wed, 4 Oct 2023 14:23:16 +0200
From: Simon Horman <horms@...nel.org>
To: Petr Machata <petrm@...dia.com>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, Ido Schimmel <idosch@...dia.com>,
	Amit Cohen <amcohen@...dia.com>, mlxsw@...dia.com
Subject: Re: [PATCH net-next 0/5] mlxsw: Control the order of blocks in ACL
 region

On Tue, Oct 03, 2023 at 01:25:25PM +0200, Petr Machata wrote:
> Amit Cohen writes:
> 
> For 12 key blocks in the A-TCAM, rules are split into two records, which
> constitute two lookups. The two records are linked using a
> "large entry key ID".
> 
> Due to a Spectrum-4 hardware issue, KVD entries that correspond to key
> blocks 0 to 5 of 12 key blocks will be placed in the same KVD pipe if they
> only differ in their "large entry key ID", as it is ignored. This results
> in a reduced scale, we can insert less than 20k filters and get an error:
> 
>     $ tc -b flower.batch
>     RTNETLINK answers: Input/output error
>     We have an error talking to the kernel
> 
> To reduce the probability of this issue, we can place key blocks with
> high entropy in blocks 0 to 5. The idea is to place blocks that are often
> changed in blocks 0 to 5, for example, key blocks that match on IPv4
> addresses or the LSBs of IPv6 addresses. Such placement will reduce the
> probability of these blocks to be same.
> 
> Mark several blocks with 'high_entropy' flag and place them in blocks 0
> to 5. Note that the list of the blocks is just a suggestion, I will verify
> it with architects.
> 
> Currently, there is a one loop that chooses which blocks should be used
> for a given list of elements and fills the blocks - when a block is
> chosen, it fills it in the region. To be able to control the order of
> the blocks, separate between searching blocks and filling them. Several
> pre-changes are required.
> 
> Patch set overview:
> Patch #1 marks several blocks with 'high_entropy' flag.
> Patches #2-#4 prepare the code for filling blocks at the end of the search.
> Patch #5 changes the loop to just choose the blocks and fill the blocks at
> the end.
> 
> Amit Cohen (5):
>   mlxsw: Mark high entropy key blocks
>   mlxsw: core_acl_flex_keys: Add a bitmap to save which blocks are
>     chosen
>   mlxsw: core_acl_flex_keys: Save chosen elements per block
>   mlxsw: core_acl_flex_keys: Save chosen elements in all blocks per
>     search
>   mlxsw: core_acl_flex_keys: Fill blocks with high entropy first
> 
>  .../mellanox/mlxsw/core_acl_flex_keys.c       | 64 +++++++++++++++++--
>  .../mellanox/mlxsw/core_acl_flex_keys.h       |  9 +++
>  .../mellanox/mlxsw/spectrum_acl_flex_keys.c   | 12 ++--
>  3 files changed, 72 insertions(+), 13 deletions(-)

For series,

Reviewed-by: Simon Horman <horms@...nel.org>