netdev - Re: [v1 PATCH 1/14] rhashtable: Remove shift from bucket

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Date:	Wed, 18 Mar 2015 21:12:10 +1100
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	"'tgraf@...g.ch'" <tgraf@...g.ch>
Cc:	David Laight <David.Laight@...LAB.COM>,
	David Miller <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [v1 PATCH 1/14] rhashtable: Remove shift from bucket_table

On Wed, Mar 18, 2015 at 10:08:12AM +0000, 'tgraf@...g.ch' wrote:
>
> With this fixed up I can see what you mean. So if we are
> to only do a chain length based decision, the limit would
> have to grow together with the table size.

All we could just use a flat limit of 16 since our maximum table
size is 2^32 (actually a bit less) and 16 should be plenty for
that.

Remember this limit is only there to detect when somebody has
stolen our secret is trying to DoS us.  So if we can keep them
under 16 per-bucket it should be sufficient to defeat any attack.

Of course I will also add a patch to limit the number of elements
to the table size (so maximum utilisation is 100%).  This will come
after we allow insertions to fail.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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