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Date: Tue, 17 Mar 2009 17:05:35 +1100 From: Nick Piggin <nickpiggin@...oo.com.au> 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 On Tuesday 17 March 2009 12:32:20 Mathieu Desnoyers wrote: > Hi, > > I am trying to get access to some non-x86 hardware to run some atomic > primitive benchmarks for a paper on LTTng I am preparing. That should be > useful to argue about performance benefit of per-cpu atomic operations > vs interrupt disabling. I would like to run the following benchmark > module on CONFIG_SMP : > > - PowerPC > - MIPS > - ia64 > - alpha > > usage : > make > insmod test-cmpxchg-nolock.ko > insmod: error inserting 'test-cmpxchg-nolock.ko': -1 Resource temporarily > unavailable dmesg (see dmesg output) > > If some of you would be kind enough to run my test module provided below > and provide the results of these tests on a recent kernel (2.6.26~2.6.29 > should be good) along with their cpuinfo, I would greatly appreciate. > > Here are the CAS results for various Intel-based architectures : > > Architecture | Speedup | CAS | > Interrupts | > > | (cli + sti) / local cmpxchg | local | sync | Enable > | (sti) | Disable (cli) > > --------------------------------------------------------------------------- >---------------------- Intel Pentium 4 | 5.24 | > 25 | 81 | 70 | 61 | AMD Athlon(tm)64 X2 | 4.57 > | 7 | 17 | 17 | 15 | Intel > Core2 | 6.33 | 6 | 30 | 20 > | 18 | Intel Xeon E5405 | 5.25 | 8 > | 24 | 20 | 22 | > > The benefit expected on PowerPC, ia64 and alpha should principally come > from removed memory barriers in the local primitives. Benefit versus what? I think all of those architectures can do SMP atomic compare exchange sequences without barriers, can't they? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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