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Date:	Fri, 1 May 2015 12:37:25 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Thomas Graf <tgraf@...g.ch>
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 Fri, May 01, 2015 at 06:30:25AM +0200, Thomas Graf wrote:
>
> 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.

It's just a matter of logical consistency.  At 75% if you grow by
a factor of 4, you get 18.75% utilisation which is way below the
30% shrink threshold.

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

Even at 100%, a factor of 4 leads you to 25% which is less than 30%.

Perhaps we could lower the shrink thresholds? Alternatively, only
grow quickly if automatic shrinking is disabled.  After all, the one
case that's inspring all of this, netlink really wants to grow
quickly as well as only shrink at specific points in time.

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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