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

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Message-ID: <20150317112726.GC11671@gondor.apana.org.au>
Date:	Tue, 17 Mar 2015 22:27:26 +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 Tue, Mar 17, 2015 at 11:22:03AM +0000, tgraf@...g.ch wrote:
>
> Not sure I understand the downside of a bucket length based grow
> decision with optional forced rehashing plus synchroneous table
> realloc if we hit a 2nd watermark as you proposed earlier. Shouldn't
> we consider deterministic lookup and insert behaviour more important
> than overall table utilization? Given the rehashing, the grow decision
> should not be attackable.

Do you really want to double the table size when 0.1% of the buckets
have a chain length > 4 but still < 16?

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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