Messages in this thread | | | Date | Mon, 16 Mar 2009 20:37:05 -0700 (PDT) | Subject | Re: cli/sti vs local_cmpxchg and local_add_return | From | David Miller <> |
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From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Date: Mon, 16 Mar 2009 21:32:20 -0400
> 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's sparc64, but cycles is always computed as zero.
Probably that's because get_cycles() on sparc64 counts system bus clock cycles, not CPU cycles, and you the loop iteration isn't expensive enough to get a system clock tick in.
This is a dual UltraSPARC-IIIi at 1.2 GHz
[1052598.484452] test init [1052598.486230] test results: time for baseline [1052598.487878] number of loops: 20000 [1052598.489485] total time: 752 [1052598.491061] -> baseline takes 0 cycles [1052598.492649] test end [1052598.494874] test results: time for locked cmpxchg [1052598.496460] number of loops: 20000 [1052598.498005] total time: 7879 [1052598.499521] -> locked cmpxchg takes 0 cycles [1052598.501060] test end [1052598.503194] test results: time for non locked cmpxchg [1052598.504733] number of loops: 20000 [1052598.506213] total time: 7879 [1052598.507722] -> non locked cmpxchg takes 0 cycles [1052598.509229] test end [1052598.511347] test results: time for locked add return [1052598.512821] number of loops: 20000 [1052598.514265] total time: 8254 [1052598.515682] -> locked add return takes 0 cycles [1052598.517130] test end [1052598.519427] test results: time for non locked add return [1052598.520850] number of loops: 20000 [1052598.522230] total time: 11259 [1052598.523561] -> non locked add return takes 0 cycles [1052598.524939] test end [1052598.526393] test results: time for enabling interrupts (STI) [1052598.527767] number of loops: 20000 [1052598.529085] total time: 1877 [1052598.530373] -> enabling interrupts (STI) takes 0 cycles [1052598.531713] test end [1052598.533240] test results: time for disabling interrupts (CLI) [1052598.534594] number of loops: 20000 [1052598.535892] total time: 3189 [1052598.537189] -> disabling interrupts (CLI) takes 0 cycles [1052598.538551] test end [1052598.540176] test results: time for disabling/enabling interrupts (STI/CLI) [1052598.541579] number of loops: 20000 [1052598.542900] total time: 3940 [1052598.544207] -> enabling/disabling interrupts (STI/CLI) takes 0 cycles [1052598.545595] test end
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