On Wed, Sep 07, 2016 at 10:32:01AM +0530, Viresh Kumar wrote: > On 01-09-16, 15:21, Andreas Herrmann wrote:
---8<--- > > I started with the value return as "nominal latency" for PCC. This > > was 300000 ns on the test system and made things worse. I've tested > > other values as well unitl I've found a local optimium at 45000ns but > > performance was lower in comparison to when I've applied my hack. > > Can you try to use kernel tracer (ftrace) and see how the frequencies > are getting changed and at what frequency. Below is some trace data. I hope it is of some help. (A) - sampling 10s period when system is idle (B) - sampling 10s period when system partially loaded (kernel compilation using 2 jobs) (1) 4.8-rc5 (2) 4.8-rc5 with my patch (reintro of deadband effect within pcc-cpufreq) (3) 4.8-rc5 with reversal of 6393d6a102 (cpufreq: ondemand: Eliminate the deadband effect) Let me know whether you are looking for other trace data wrt this issue. Thanks, Andreas --- (A)-(1) # Total Lost Samples: 0 # Samples: 41 of event 'power:cpu_frequency' # Event count (approx.): 41 # Overhead Command Shared Object Symbol # ........ ............ ................ ............................. 39.02% kworker/14:1 [kernel.vmlinux] [k] cpufreq_notify_transition 29.27% kworker/0:0 [kernel.vmlinux] [k] cpufreq_notify_transition 19.51% kworker/10:1 [kernel.vmlinux] [k] cpufreq_notify_transition 7.32% kworker/5:2 [kernel.vmlinux] [k] cpufreq_notify_transition 2.44% kworker/23:2 [kernel.vmlinux] [k] cpufreq_notify_transition 2.44% kworker/40:1 [kernel.vmlinux] [k] cpufreq_notify_transition (A)-(2) # Total Lost Samples: 0 # Samples: 6 of event 'power:cpu_frequency' # Event count (approx.): 6 # Overhead Command Shared Object Symbol # ........ ............ ................ ............................. 33.33% kworker/1:2 [kernel.vmlinux] [k] cpufreq_notify_transition 16.67% kworker/16:1 [kernel.vmlinux] [k] cpufreq_notify_transition 16.67% kworker/22:1 [kernel.vmlinux] [k] cpufreq_notify_transition 16.67% kworker/26:1 [kernel.vmlinux] [k] cpufreq_notify_transition 16.67% kworker/33:1 [kernel.vmlinux] [k] cpufreq_notify_transition (A)-(3) # Total Lost Samples: 0 # Samples: 7 of event 'power:cpu_frequency' # Event count (approx.): 7 # Overhead Command Shared Object Symbol # ........ ............ ................ ............................. 28.57% kworker/58:1 [kernel.vmlinux] [k] cpufreq_notify_transition 14.29% kworker/19:2 [kernel.vmlinux] [k] cpufreq_notify_transition 14.29% kworker/20:2 [kernel.vmlinux] [k] cpufreq_notify_transition 14.29% kworker/22:2 [kernel.vmlinux] [k] cpufreq_notify_transition 14.29% kworker/23:1 [kernel.vmlinux] [k] cpufreq_notify_transition 14.29% kworker/35:1 [kernel.vmlinux] [k] cpufreq_notify_transition --- (B)-(1) # Total Lost Samples: 0 # Samples: 2K of event 'power:cpu_frequency' # Event count (approx.): 2382 # Overhead Command Shared Object Symbol # ........ ............ ................ ............................. 5.75% kworker/0:0 [kernel.vmlinux] [k] cpufreq_notify_transition 4.16% kworker/12:2 [kernel.vmlinux] [k] cpufreq_notify_transition 3.11% kworker/17:1 [kernel.vmlinux] [k] cpufreq_notify_transition 2.94% kworker/2:1 [kernel.vmlinux] [k] cpufreq_notify_transition 2.73% kworker/19:1 [kernel.vmlinux] [k] cpufreq_notify_transition ... (B)-(2) # Total Lost Samples: 0 # Samples: 320 of event 'power:cpu_frequency' # Event count (approx.): 320 # Overhead Command Shared Object Symbol # ........ ............ ................ ............................. 4.69% kworker/56:1 [kernel.vmlinux] [k] cpufreq_notify_transition 4.06% kworker/12:1 [kernel.vmlinux] [k] cpufreq_notify_transition 4.06% kworker/28:1 [kernel.vmlinux] [k] cpufreq_notify_transition 4.06% kworker/6:2 [kernel.vmlinux] [k] cpufreq_notify_transition 3.75% kworker/32:2 [kernel.vmlinux] [k] cpufreq_notify_transition ... (B)-(3) # Total Lost Samples: 0 # Samples: 333 of event 'power:cpu_frequency' # Event count (approx.): 333 # Overhead Command Shared Object Symbol # ........ ............ ................ ............................. 4.80% kworker/51:1 [kernel.vmlinux] [k] cpufreq_notify_transition 4.50% kworker/39:1 [kernel.vmlinux] [k] cpufreq_notify_transition 4.20% kworker/47:1 [kernel.vmlinux] [k] cpufreq_notify_transition 3.90% kworker/59:1 [kernel.vmlinux] [k] cpufreq_notify_transition 3.90% kworker/7:2 [kernel.vmlinux] [k] cpufreq_notify_transition ... --- With (1) pcc-cpufreq tries to set pretty much every frequency even if the system is idle, e.g. here is the start of (perf script output) from (A)-(1): kworker/5:2 904 [005] 255.778343: power:cpu_frequency: state=1216000 cpu_id=5 kworker/5:2 904 [005] 255.794382: power:cpu_frequency: state=1264000 cpu_id=5 kworker/5:2 904 [005] 256.102400: power:cpu_frequency: state=1200000 cpu_id=5 kworker/10:1 171 [010] 258.010362: power:cpu_frequency: state=2224000 cpu_id=10 kworker/10:1 171 [010] 258.026366: power:cpu_frequency: state=1264000 cpu_id=10 kworker/10:1 171 [010] 258.594514: power:cpu_frequency: state=1200000 cpu_id=10 kworker/10:1 171 [010] 258.618417: power:cpu_frequency: state=1232000 cpu_id=10 kworker/10:1 171 [010] 258.634409: power:cpu_frequency: state=1264000 cpu_id=10 kworker/10:1 171 [010] 258.674467: power:cpu_frequency: state=1200000 cpu_id=10 kworker/10:1 171 [010] 258.730486: power:cpu_frequency: state=1216000 cpu_id=10 kworker/40:1 388 [040] 258.730999: power:cpu_frequency: state=1200000 cpu_id=40 kworker/23:2 775 [023] 258.731504: power:cpu_frequency: state=1200000 cpu_id=23 kworker/14:1 178 [014] 258.732013: power:cpu_frequency: state=1216000 cpu_id=14 kworker/10:1 171 [010] 258.906434: power:cpu_frequency: state=1200000 cpu_id=10 kworker/14:1 178 [014] 258.970500: power:cpu_frequency: state=1200000 cpu_id=14 kworker/14:1 178 [014] 258.998440: power:cpu_frequency: state=1232000 cpu_id=14 kworker/14:1 178 [014] 259.034490: power:cpu_frequency: state=1200000 cpu_id=14 kworker/14:1 178 [014] 259.095089: power:cpu_frequency: state=1216000 cpu_id=14 kworker/14:1 178 [014] 259.270470: power:cpu_frequency: state=1200000 cpu_id=14 ...