linux-kernel - Re: [bisected] e341694e3eb5 netlink_lookup() rcu conversion causes latencies

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Message-Id: <20141011.190829.876705206204533685.davem@davemloft.net>
Date:	Sat, 11 Oct 2014 19:08:29 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	tgraf@...g.ch
Cc:	eric.dumazet@...il.com, heiko.carstens@...ibm.com,
	sasha.levin@...cle.com, paulmck@...ux.vnet.ibm.com,
	nikolay@...hat.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, braunu@...ibm.com
Subject: Re: [bisected] e341694e3eb5 netlink_lookup() rcu conversion causes
 latencies

From: Thomas Graf <tgraf@...g.ch>
Date: Sat, 11 Oct 2014 23:25:14 +0100

> I think the issue here is obvious and a fix is on the way to move
> the insertion and removal to a worker to no longer require the
> synchronize_rcu().
> 
> What bothers me is that the synchronize_rcu() should only occur
> on expand/shrink and not for every table update. The default table
> size is 64.

Not true, every netlink socket release incurs a synchronize_net()
now, because we added such a call to netlink_release().

I specifically brought this up to as a possible problem when the
changes went in...
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