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Date: Thu, 23 Apr 2009 11:29:28 -0700
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org,
       netdev@vger.kernel.org, netfilter-devel@vger.kernel.org,
       akpm@linux-foundation.org, davem@davemloft.net, dada1@cosmosbay.com,
       zbr@ioremap.net, jeff.chua.linux@gmail.com, paulus@samba.org,
       laijs@cn.fujitsu.com, jengelh@medozas.de, r000n@r000n.net,
       benh@kernel.crashing.org, mathieu.desnoyers@polymtl.ca
Subject: Re: [PATCH RFC] v1 expedited "big hammer" RCU grace periods
Message-ID: <20090423182928.GF6877@linux.vnet.ibm.com>
Reply-To: paulmck@linux.vnet.ibm.com
References: <20090423052520.GA13036@linux.vnet.ibm.com> <20090423075436.GB22606@elte.hu> <20090423153402.GC6877@linux.vnet.ibm.com> <alpine.LFD.2.00.0904230842571.3101@localhost.localdomain>
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On Thu, Apr 23, 2009 at 08:47:02AM -0700, Linus Torvalds wrote:
> 
> 
> On Thu, 23 Apr 2009, Paul E. McKenney wrote:
> > 
> > Hmmm...  I need to ask Jeff Chua what HZ he was running with.  Because if
> > there was some read-side critical section soaking up 30 milliseconds,
> > all that hammering will do is slow things down...
> 
> The original bug report comes from simply bootup:
> 
>   "I'm loading all the firewall rules during boot-up and this 6 secs 
>    slowness is really not very nice to wait for."
> 
> IOW, the problematic case likely effectively has _nothing_ else going on. 
> Sure, there might be some parallelism (the bootup scripts are getting 
> better for that), but hopefully not 6 seconds worth, and not likely any 
> complex critical sections.

Sounds good to me!  ;-)

							Thanx, Paul