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Date: Mon, 25 Aug 2008 10:44:03 -0500
From: Christoph Lameter <cl@linux-foundation.org>
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CC: Peter Zijlstra <peterz@infradead.org>,
       Pekka Enberg <penberg@cs.helsinki.fi>, Ingo Molnar <mingo@elte.hu>,
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Subject: Re: [PATCH 2/2] smp_call_function: use rwlocks on queues rather	than
 rcu
References: <84144f020808220006n25d684b1n9db306ddc4f58c4c@mail.gmail.com> <48AEC6B2.1080701@linux-foundation.org> <20080822151156.GA6744@linux.vnet.ibm.com> <48AEF3FD.70906@linux-foundation.org> <20080822182915.GG6744@linux.vnet.ibm.com> <48AF0735.60402@linux-foundation.org> <20080822195226.GJ6744@linux.vnet.ibm.com> <48AF1B81.3050806@linux-foundation.org> <20080822205339.GK6744@linux.vnet.ibm.com> <1219660291.8515.20.camel@twins> <20080825151220.GA6745@linux.vnet.ibm.com>
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Paul E. McKenney wrote:

> But I am not sure that this gets the grace periods to go fast enough to
> cover Christoph's use case -- he seems to be in a "faster is better"
> space rather than in an "at least this fast" space.  Still, it would
> likely help in some important cases.

I think there was an AIM9 regression in the close/open tests when the struct
file was switched to RCU. That test could be run with various intervals to
figure out if a shorter RCU period is beneficial and how short an RCU period
is needed to avoid the regression.