netdev - Re: [PATCH net-next 1/2] bridge: Add a limit on FDB entries

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Message-ID: <c4602c0f-76b1-c9a4-f7f1-1f5a02a56564@blackwall.org>
Date: Tue, 16 May 2023 11:30:53 +0300
From: Nikolay Aleksandrov <razor@...ckwall.org>
To: Johannes Nixdorf <jnixdorf-oss@....de>
Cc: netdev@...r.kernel.org, bridge@...ts.linux-foundation.org,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Roopa Prabhu <roopa@...dia.com>
Subject: Re: [PATCH net-next 1/2] bridge: Add a limit on FDB entries

On 16/05/2023 11:12, Johannes Nixdorf wrote:
[snip]
>>>  		return -EMSGSIZE;
>>>  
>>>  #ifdef CONFIG_BRIDGE_VLAN_FILTERING
>>> diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
>>> index 2119729ded2b..64fb359c6e3e 100644
>>> --- a/net/bridge/br_private.h
>>> +++ b/net/bridge/br_private.h
>>> @@ -494,6 +494,8 @@ struct net_bridge {
>>>  #endif
>>>  
>>>  	struct rhashtable		fdb_hash_tbl;
>>> +	u32				fdb_n_entries;
>>> +	u32				fdb_max_entries;
>>
>> These are not critical, so I'd use 4 byte holes in net_bridge and pack it better
>> instead of making it larger.
> 
> For a v2 I now moved it into (conditional) holes now in front of
> CONFIG_BRIDGE_VLAN_FILTERING (only a hole if it is enabled) and
> CONFIG_SWITCHDEV (only a hole if it is disabled). I could not find any
> other holes, but please tell me if you had any others in mind.
> 

Just please don't add them in the first 64 bytes (first cache line) as we use that
in the hot path and keep it for variables used there. I'd say use any of the other
4 byte holes and just add both, so another 4 byte hole would be left after the second one.

>>>  	struct list_head		port_list;
>>>  #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
>>>  	union {
>>
> 
> Thanks for your detailed feedback.