linux-kernel - Re: [PATCH net-next 3/3] nftables: Convert nft

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Message-ID: <20140801103901.GC7331@casper.infradead.org>
Date:	Fri, 1 Aug 2014 11:39:01 +0100
From:	Thomas Graf <tgraf@...g.ch>
To:	Patrick McHardy <kaber@...sh.net>
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, paulmck@...ux.vnet.ibm.com,
	josh@...htriplett.org, challa@...ronetworks.com,
	walpole@...pdx.edu, dev@...nvswitch.org, tklauser@...tanz.ch,
	netfilter-devel@...r.kernel.org
Subject: Re: [PATCH net-next 3/3] nftables: Convert nft_hash to use generic
 rhashtable

On 08/01/14 at 11:17am, Patrick McHardy wrote:
> On 1. August 2014 09:52:00 GMT+01:00, Thomas Graf <tgraf@...g.ch> wrote:
> >If the set size is known in advance, the table is sized accordingly,
> >otherwise the table size will default to 64. This is a slight change
> >in behaviour as previously the default was 4 which eventually required
> >many expansion iterations.
> 
> That's assuming a sufficient number of entries will be added. I think there
> will be many cases in nftables where the number will be lower. Since
> expansion is not very expansive this number was chosen very deliberately
> and I'd prefer to keep it.
> 
> Other than that:
> 
> Acked-by: Patrick McHardy <kaber@...sh.net>

OK, I will change the nft_hash default size back to 4.

I think the expansion is more expensive than it looks though as we
are potentially calling synchronize_rcu() multiple times while
holding a mutex to protect from concurrent mutations.
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