netdev - Re: [PATCH net-next 5/5] tipc: convert tipc reference table to use generic rhashtable

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Date:	Tue, 6 Jan 2015 09:42:51 +0000
From:	Thomas Graf <tgraf@...g.ch>
To:	Ying Xue <ying.xue@...driver.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	jon.maloy@...csson.com, Paul.Gortmaker@...driver.com,
	erik.hugne@...csson.com, tipc-discussion@...ts.sourceforge.net
Subject: Re: [PATCH net-next 5/5] tipc: convert tipc reference table to use
 generic rhashtable

On 01/06/15 at 03:23pm, Ying Xue wrote:
> As tipc reference table is statically allocated, its memory size
> requested on stack initialization stage is quite big even if the
> maximum port number is just restricted to 8191 currently, however,
> the number already becomes insufficient in practice. But if the
> maximum ports is allowed to its theory value - 2^32, its consumed
> memory size will reach a ridiculously unacceptable value. Apart from
> this, heavy tipc users spend a considerable amount of time in
> tipc_sk_get() due to the read-lock on ref_table_lock.
> 
> If tipc reference table is converted with generic rhashtable, above
> mentioned both disadvantages would be resolved respectively: making
> use of the new resizable hash table can avoid locking on the lookup;
> smaller memory size is required at initial stage, for example, 256
> hash bucket slots are requested at the beginning phase instead of
> allocating the entire 8191 slots in old mode. The hash table will
> grow if entries exceeds 75% of table size up to a total table size
> of 1M, and it will automatically shrink if usage falls below 30%,
> but the minimum table size is allowed down to 256.
> 
> Also converts ref_table_lock to a separate mutex to protect hash table
> mutations on write side. Lastly defers the release of the socket
> reference using call_rcu() to allow using an RCU read-side protected
> call to rhashtable_lookup().
> 
> Signed-off-by: Ying Xue <ying.xue@...driver.com>
> Acked-by: Jon Maloy <jon.maloy@...csson.com>
> Acked-by: Erik Hugne <erik.hugne@...csson.com>
> Cc: Thomas Graf <tgraf@...g.ch>

The rhashtable usage looks good to me. I assume the TIPC maintainers
have reviewed the other pieces.

Acked-by: Thomas Graf <tgraf@...g.ch>
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