Date: Sat, 21 Feb 2015 10:00:02 -0800
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Arjan van de Ven <arjan@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>, linux-kernel@vger.kernel.org,
        mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com,
        akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
        josh@joshtriplett.org, tglx@linutronix.de, rostedt@goodmis.org,
        dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com,
        fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com
Subject: Re: [PATCH tip/core/rcu 0/4] Programmatic nestable expedited grace
 periods
Message-ID: <20150221180002.GU5745@linux.vnet.ibm.com>
Reply-To: paulmck@linux.vnet.ibm.com
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 <20150220165409.GU5029@twins.programming.kicks-ass.net>
 <20150220171442.GM5745@linux.vnet.ibm.com>
 <54E76FB7.4060005@linux.intel.com>
 <20150220182745.GN5745@linux.vnet.ibm.com>
 <54E8A986.4090302@linux.intel.com>
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On Sat, Feb 21, 2015 at 07:51:34AM -0800, Arjan van de Ven wrote:
> >>
> >>there's a few others as well that I'm chasing down...
> >>.. but the flip side, prior to running ring 3 code, why NOT do fast expedites?
> >
> >It would be good to have before-and-after measurements of actual
> >boot time.  Are these numbers available?
> 
> 
> To show the boot time, I'm using the timestamp of the "Write protecting" line,
> that's pretty much the last thing we print prior to ring 3 execution.
> 
> A kernel with default RCU behavior (inside KVM, only virtual devices) looks like this:
> 
> [    0.038724] Write protecting the kernel read-only data: 10240k
> 
> a kernel with expedited RCU (using the command line option, so that I don't have
> to recompile between measurements and thus am completely oranges-to-oranges)
> 
> [    0.031768] Write protecting the kernel read-only data: 10240k
> 
> which, in percentage, is an 18% improvement.

Thank you, will repost with this info.

							Thanx, Paul

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