linux-kernel - Re: [PATCH RFC] v1 expedited "big hammer" RCU grace periods

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Message-ID: <20090423182928.GF6877@linux.vnet.ibm.com>
Date:	Thu, 23 Apr 2009 11:29:28 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
	akpm@...ux-foundation.org, davem@...emloft.net,
	dada1@...mosbay.com, zbr@...emap.net, jeff.chua.linux@...il.com,
	paulus@...ba.org, laijs@...fujitsu.com, jengelh@...ozas.de,
	r000n@...0n.net, benh@...nel.crashing.org,
	mathieu.desnoyers@...ymtl.ca
Subject: Re: [PATCH RFC] v1 expedited "big hammer" RCU grace periods

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
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