[Nexus 6P Original Android Development] hinxnz:
AFAIK perfd is proprietary and when disabling it you'll also see this below in logcat.

03-20 10:35:06.396: W/perfd (20635): type=1400 audit(0.0:112386): avc: denied { write } for name="run" dev="sysfs" ino=10969 scontext=u:r:perfd:s0 tcontext=u:object_r:sysfs:s0 tclass=file permissive=0
03-20 10:35:06.396: W/perfd (20635): type=1400 audit(0.0:112387): avc: denied { write } for name="sleep_millisecs" dev="sysfs" ino=10967 scontext=u:r:perfd:s0 tcontext=u:object_r:sysfs:s0 tclass=file permissive=0
03-20 10:35:06.396: W/perfd (20635): type=1400 audit(0.0:112388): avc: denied { write } for name="pages_to_scan" dev="sysfs" ino=10968 scontext=u:r:perfd:s0 tcontext=u:object_r:sysfs:s0 tclass=file permissive=0
03-20 10:35:06.399: W/perfd (20635): type=1400 audit(0.0:112389): avc: denied { write } for name="hispeed_freq" dev="sysfs" ino=25259 scontext=u:r:perfd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=file permissive=0
03-20 10:35:06.399: W/perfd (20635): type=1400 audit(0.0:112390): avc: denied { write } for name="above_hispeed_delay" dev="sysfs" ino=25258 scontext=u:r:perfd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=file permissive=0
03-20 10:35:06.399: W/perfd (20635): type=1400 audit(0.0:112391): avc: denied { write } for name="go_hispeed_load" dev="sysfs" ino=25260 scontext=u:r:perfd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=file permissive=0
03-20 10:35:06.399: W/perfd (20635): type=1400 audit(0.0:112392): avc: denied { write } for name="target_loads" dev="sysfs" ino=25257 scontext=u:r:perfd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=file permissive=0
03-20 10:35:06.399: W/perfd (20635): type=1400 audit(0.0:112393): avc: denied { write } for name="default_pwrlevel" dev="sysfs" ino=13713 scontext=u:r:perfd:s0 tcontext=u:object_r:sysfs:s0 tclass=file permissive=0
03-20 10:35:06.399: W/perfd (20635): type=1400 audit(0.0:112394): avc: denied { write } for name="min_freq" dev="sysfs" ino=19637 scontext=u:r:perfd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=file permissive=0
03-20 10:35:06.399: W/perfd (20635): type=1400 audit(0.0:112395): avc: denied { write } for name="decay_rate" dev="sysfs" ino=25600 scontext=u:r:perfd:s0 tcontext=u:object_r:sysfs:s0 tclass=file permissive=0
03-20 10:35:06.399: W/perfd (20635): type=1400 audit(0.0:112396): avc: denied { write } for name="io_percent" dev="sysfs" ino=25601 scontext=u:r:perfd:s0 tcontext=u:object_r:sysfs:s0 tclass=file permissive=0
03-20 10:35:06.399: W/perfd (20635): type=1400 audit(0.0:112397): avc: denied { write } for name="hispeed_freq" dev="sysfs" ino=25259 scontext=u:r:perfd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=file permissive=0
03-20 10:35:06.399: W/perfd (20635): type=1400 audit(0.0:112398): avc: denied { write } for name="above_hispeed_delay" dev="sysfs" ino=25258 scontext=u:r:perfd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=file permissive=0
03-20 10:35:06.399: W/perfd (20635): type=1400 audit(0.0:112399): avc: denied { write } for name="target_loads" dev="sysfs" ino=25257 scontext=u:r:perfd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=file permissive=0
03-20 10:35:06.399: W/perfd (20635): type=1400 audit(0.0:112400): avc: denied { write } for name="min_sample_time" dev="sysfs" ino=25261 scontext=u:r:perfd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=file permissive=0
03-20 10:35:06.399: W/perfd (20635): type=1400 audit(0.0:112401): avc: denied { write } for name="go_hispeed_load" dev="sysfs" ino=25260 scontext=u:r:perfd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=file permissive=0
03-20 10:35:06.399: W/perfd (20635): type=1400 audit(0.0:112402): avc: denied { write } for name="max_freq_hysteresis" dev="sysfs" ino=25270 scontext=u:r:perfd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=file permissive=0
03-20 10:35:06.399: W/perfd (20635): type=1400 audit(0.0:112403): avc: denied { write } for name="timer_rate" dev="sysfs" ino=25262 scontext=u:r:perfd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=file permissive=0
03-20 10:35:06.399: W/perfd (20635): type=1400 audit(0.0:112404): avc: denied { write } for name="timer_slack" dev="sysfs" ino=25263 scontext=u:r:perfd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=file permissive=0
03-20 10:35:06.399: W/perfd (20635): type=1400 audit(0.0:112405): avc: denied { write } for name="io_is_busy" dev="sysfs" ino=25267 scontext=u:r:perfd:s0 tcontext=u:object_r:sysfs_devices_system_cpu:s0 tclass=file permissive=0