netdev - Re: [PATCH net-next 2/2] rhashtable: Quick initial growth of tables

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Message-ID: <20150501043025.GB26676@pox.localdomain>
Date:	Fri, 1 May 2015 06:30:25 +0200
From:	Thomas Graf <tgraf@...g.ch>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	davem@...emloft.net, netdev@...r.kernel.org, kaber@...sh.net
Subject: Re: [PATCH net-next 2/2] rhashtable: Quick initial growth of tables

On 05/01/15 at 07:45am, Herbert Xu wrote:
> Thomas Graf <tgraf@...g.ch> wrote:
> > Grow the table quicker than 2x in the beginning to avoid long chains
> > of rehashes. The effect is observable in the self-test where table
> > jumps are reduced to a minimum after a lot of entries have been added
> > in a short period of time. The iterator is able to get a consistent
> > view most of the time.
> > 
> > Signed-off-by: Thomas Graf <tgraf@...g.ch>
> 
> Wouldn't automatic shrinking immediately undo your quick growth?

Yes, that can happen. Since shrinks are ordered to the end of the
chain it is often the case that enough entries have been added so the
shrink is not carried out in the end. Obviously this is also not the
case if no entries are actually removed.

What about we apply quick growing on >100% utilization? It is a
clear indication that we are growing rapidly.
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