netdev - Re: [PATCH net-next] rhashtable: kill ht->shift atomic operations

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Message-ID: <20150312144308.GB5378@casper.infradead.org>
Date:	Thu, 12 Mar 2015 14:43:08 +0000
From:	Thomas Graf <tgraf@...g.ch>
To:	Daniel Borkmann <daniel@...earbox.net>
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	Ying Xue <ying.xue@...driver.com>
Subject: Re: [PATCH net-next] rhashtable: kill ht->shift atomic operations

On 03/12/15 at 03:28pm, Daniel Borkmann wrote:
> Commit c0c09bfdc415 ("rhashtable: avoid unnecessary wakeup for worker
> queue") changed ht->shift to be atomic, which is actually unnecessary.
> 
> Instead of leaving the current shift in the core rhashtable structure,
> it can be cached inside the individual bucket tables.
> 
> There, it will only be initialized once during a new table allocation
> in the shrink/expansion slow path, and from then onward it stays immutable
> for the rest of the bucket table liftime.
> 
> That allows shift to be non-atomic. The patch also moves hash_rnd
> management into the table setup. The rhashtable structure now consumes
> 3 instead of 4 cachelines.
> 
> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
> Cc: Ying Xue <ying.xue@...driver.com>

Very nice

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