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

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Message-Id: <20150323.124434.1526209682898584518.davem@davemloft.net>
Date:	Mon, 23 Mar 2015 12:44:34 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	tgraf@...g.ch
Cc:	herbert@...dor.apana.org.au, eric.dumazet@...il.com,
	kaber@...sh.net, josh@...htriplett.org, paulmck@...ux.vnet.ibm.com,
	netdev@...r.kernel.org
Subject: Re: [v2 PATCH 7/10] rhashtable: Disable automatic shrinking

From: Thomas Graf <tgraf@...g.ch>
Date: Mon, 23 Mar 2015 08:33:19 +0000

> I don't get why almost nobody would want shrinking. I agree that for
> tables like TCP hash tables, once you have grown you want to keep that
> table size because the load is likely to come back. But we will also
> have lots of users such as the Netlink socket with a table per protocol
> where not shrinking results in giving the user the ability to waste
> memory indefinitely for no gain.

The user can't do this with TCP?  Why is netlink only susceptible?

The only plausible argument for shrinking I've ever heard of is the
nft_hash case, and there that code can _explicitly_ ask for a shrink
after it has made a major table modification.

That puts all of the smarts for when to shrink where the knowledge
resides, and in this case that's the user.
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