Messages in this thread | | | From | Nick Piggin <> | Subject | Re: cli/sti vs local_cmpxchg and local_add_return | Date | Tue, 17 Mar 2009 17:05:35 +1100 |
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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?
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