netdev - Re: Scalability of interface creation and deletion

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Message-ID: <BANLkTi=A=iV8eKOH7uqaL8g7hGpjt7XWVw@mail.gmail.com>
Date:	Tue, 10 May 2011 00:46:05 +0300
From:	Octavian Purdila <tavi.purdila@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Alex Bligh <alex@...x.org.uk>, netdev@...r.kernel.org
Subject: Re: Scalability of interface creation and deletion

On Sat, May 7, 2011 at 6:54 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:

>
> synchronize_rcu() calls are not consuming cpu, they just _wait_
> rcu grace period.
>
> I suggest you read Documentation/RCU files if you really want to :)
>
> If you want to check how expensive it is, its quite easy:
> add a trace in synchronize_net()
>
<snip>

I proposed adding a "wait" software counter to perf [1] a while ago,
which would allow people identify sync_rcu hotspots:

http://marc.info/?l=linux-kernel&m=129188584110162

I don't know how much visibility it got, so given this context, I
thought of bringing it up again :)
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