netdev - Re: [v2 PATCH 7/10] rhashtable: Disable automatic shrinking

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Message-ID: <20150323101931.GB13000@gondor.apana.org.au>
Date:	Mon, 23 Mar 2015 21:19:32 +1100
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Thomas Graf <tgraf@...g.ch>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Patrick McHardy <kaber@...sh.net>,
	Josh Triplett <josh@...htriplett.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	netdev@...r.kernel.org
Subject: Re: [v2 PATCH 7/10] rhashtable: Disable automatic shrinking

On Mon, Mar 23, 2015 at 10:08:52AM +0000, Thomas Graf wrote:
>
> I have yet to understand the implications of multiple rehashes.
> The idea of having to traverse N tables for each insert, removal
> and lookup in a pressure situation is still frightening.

It's simple.  With only expansion you can never have more than
log N tables.

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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