linux-kernel - Re: cli/sti vs local_cmpxchg and local_add

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Date:	Tue, 17 Mar 2009 14:42:09 -0400
From:	"Alan D. Brunelle" <Alan.Brunelle@...com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
CC:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Josh Boyer <jwboyer@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, ltt-dev@...ts.casi.polymtl.ca
Subject: Re: cli/sti vs local_cmpxchg and local_add_return

Here are the results for:

processor  : 31
vendor     : GenuineIntel
arch       : IA-64
family     : 32
model      : 0
model name : Dual-Core Intel(R) Itanium(R) 2 Processor 9050
revision   : 7
archrev    : 0
features   : branchlong, 16-byte atomic ops
cpu number : 0
cpu regs   : 4
cpu MHz    : 1598.002
itc MHz    : 400.000000
BogoMIPS   : 3186.68
siblings   : 2
physical id: 196865
core id    : 1
thread id  : 0

test init
test results: time for baseline
number of loops: 20000
total time: 5002
-> baseline takes 0 cycles
test end
test results: time for locked cmpxchg
number of loops: 20000
total time: 60083
-> locked cmpxchg takes 3 cycles
test end
test results: time for non locked cmpxchg
number of loops: 20000
total time: 60002
-> non locked cmpxchg takes 3 cycles
test end
test results: time for locked add return
number of loops: 20000
total time: 155007
-> locked add return takes 7 cycles
test end
test results: time for non locked add return
number of loops: 20000
total time: 155004
-> non locked add return takes 7 cycles
test end
test results: time for enabling interrupts (STI)
number of loops: 20000
total time: 45003
-> enabling interrupts (STI) takes 2 cycles
test end
test results: time for disabling interrupts (CLI)
number of loops: 20000
total time: 59998
-> disabling interrupts (CLI) takes 2 cycles
test end
test results: time for disabling/enabling interrupts (STI/CLI)
number of loops: 20000
total time: 107274
-> enabling/disabling interrupts (STI/CLI) takes 5 cycles
test end

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