linux-kernel - Re: Question about usage of RCU in the input layer

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Message-ID: <20090322205212.GI7148@linux.vnet.ibm.com>
Date:	Sun, 22 Mar 2009 13:52:12 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Eric Dumazet <dada1@...mosbay.com>, dipankar@...ibm.com,
	linux-input@...r.kernel.org, dmitry.torokhov@...il.com,
	linux-kernel@...r.kernel.org
Subject: Re: Question about usage of RCU in the input layer

On Sun, Mar 22, 2009 at 12:46:32PM -0700, Arjan van de Ven wrote:
> On Sun, 22 Mar 2009 09:53:24 -0700
> "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> wrote:
> 
> > > > How many synchronize_rcu() calls are you seeing on the boot path?
> > > 
> > > I see 20 that hit the above code path (eg ones that wait) until
> > > userspace starts.
> > 
> > So with well-behaved readers, the full sequence would be worth
> > something like 50-60 milliseconds.
> 
> yeah it's about 10% if the total kernel boot time.. so it does start to
> matter

Half-second boot, eh?  That would indeed be impressive.

							Thanx, Paul
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