Paul,
FYI, we noticed the below changes on
git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
next.2014.04.16b
commit 10a94227ba229f1b05672754dc318a8fe7982c95 ("rcu: Update
cpu_needs_another_gp() for futures from non-NOCB CPUs")
test case: nhm4/micro/will-it-scale/lseek1
11ba5ab363b9359 10a94227ba229f1b05672754d
--------------- -------------------------
11210675 ~ 0% -2.0% 10985451 ~ 0% TOTAL will-it-scale.per_process_ops
1.24 ~ 5% -33.4% 0.83 ~ 5% TOTAL
perf-profile.cpu-cycles.trace_hardirqs_off_caller.lseek64
3.88 ~ 2% +49.0% 5.79 ~ 0% TOTAL
perf-profile.cpu-cycles.trace_hardirqs_on_thunk.lseek64
295 ~16% +27.0% 375 ~ 8% TOTAL cpuidle.C1E-NHM.usage
45061 ~ 2% +16.7% 52590 ~ 2% TOTAL cpuidle.C6-NHM.usage
1.21 ~ 4% +5.8% 1.28 ~ 4% TOTAL
perf-profile.cpu-cycles.shmem_file_llseek.sys_lseek.system_call_fastpath.lseek64
4206 ~ 1% -78.6% 900 ~ 8% TOTAL interrupts.IWI
14303 ~ 1% +26.7% 18120 ~ 1% TOTAL
interrupts.0:IO-APIC-edge.timer
3228 ~ 4% -17.2% 2672 ~ 6% TOTAL interrupts.RES
182 ~ 2% -8.1% 167 ~ 3% TOTAL time.user_time
235 ~ 2% +6.2% 250 ~ 2% TOTAL time.system_time
379471 ~ 0% +1.2% 384127 ~ 0% TOTAL interrupts.LOC
Legend:
~XX% - stddev percent
[+-]XX% - change percent
It does effectively eliminate interrupts.IWI:
interrupts.IWI
4500 ++-*-----*-------*--------------------------------------------------+
|.. *. + .*. .*..*. .*..*..*.. .*..*..*..*.*..*..*
4000 *+ *. *. *. *.. .*..*. |
3500 ++ * |
| |
3000 ++ |
2500 ++ |
| |
2000 ++ |
1500 ++ |
| |
1000 ++ O O O O O O O
500 ++ O |
| |
0 O+-O--O--O-O--O--O--O--O--O-O--O--O--O--O--O-O----------------------+
[*] bisect-good sample
[O] bisect-bad sample
Thanks,
Fengguang
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