My MBR start freezing up for over hour and I've found that my kernel reported being throttled, e.g. (this is just a sample for 2 seconds)
$ sudo fs_usage | | grep -i throttled
12:26:45 THROTTLED 0.015159 kernel_task
12:26:45 THROTTLED 0.015606 kernel_task
12:26:45 THROTTLED 0.016328 kernel_task
12:26:45 THROTTLED 0.014862 kernel_task
12:26:45 THROTTLED 0.014797 kernel_task
12:26:45 THROTTLED 0.015583 kernel_task
12:26:45 THROTTLED 0.014794 kernel_task
12:26:45 THROTTLED 0.014668 kernel_task
12:26:45 THROTTLED 0.014915 kernel_task
12:26:45 THROTTLED 0.014555 kernel_task
12:26:45 THROTTLED 0.014660 kernel_task
12:26:45 THROTTLED 0.015547 kernel_task
12:26:45 THROTTLED 0.015364 kernel_task
12:26:45 THROTTLED 0.015073 kernel_task
12:26:45 THROTTLED 0.014832 kernel_task
12:26:46 THROTTLED 0.015649 kernel_task
12:26:46 THROTTLED 0.016643 kernel_task
12:26:46 THROTTLED 0.014496 kernel_task
12:26:46 THROTTLED 0.015488 kernel_task
12:26:46 THROTTLED 0.014576 kernel_task
12:26:46 THROTTLED 0.015531 kernel_task
12:26:46 THROTTLED 0.015224 kernel_task
12:26:46 THROTTLED 0.015182 kernel_task
12:26:46 THROTTLED 0.015443 kernel_task
12:26:46 THROTTLED 0.015166 kernel_task
12:26:46 THROTTLED 0.015435 kernel_task
12:26:46 THROTTLED 0.015105 kernel_task
12:26:46 THROTTLED 0.015091 kernel_task
12:26:46 THROTTLED 0.015131 kernel_task
12:26:46 THROTTLED 0.015259 kernel_task
12:26:46 THROTTLED 0.014865 kernel_task
12:26:46 THROTTLED 0.015681 kernel_task
12:26:46 THROTTLED 0.014455 kernel_task
12:26:46 THROTTLED 0.015251 kernel_task
12:26:46 THROTTLED 0.015928 kernel_task
12:26:46 THROTTLED 0.015053 kernel_task
12:26:46 THROTTLED 0.014699 kernel_task
12:26:46 THROTTLED 0.015251 kernel_task
12:26:46 THROTTLED 0.014499 kernel_task
12:26:46 THROTTLED 0.015589 kernel_task
12:26:46 THROTTLED 0.015166 kernel_task
12:26:46 THROTTLED 0.015422 kernel_task
12:26:46 THROTTLED 0.018772 nsurlsession
12:26:46 THROTTLED 0.029125 kernel_task
12:26:46 THROTTLED 0.014671 kernel_task
12:26:46 THROTTLED 0.014763 kernel_task
12:26:46 THROTTLED 0.015114 kernel_task
12:26:46 THROTTLED 0.009341 iStat Menus
12:26:46 THROTTLED 0.008501 kernel_task
12:26:46 THROTTLED 0.014090 kernel_task
I've increased fan control to the maximum (via iStat Menus), as I've read it may be related to the high CPU temperature, but it didn't do any difference. Only killing some tasks helped a bit.
I know how to kill the tasks or restart the computer to temporary fix the problem. However I'm more interested what exactly is the kernel throttling, why this happens (why it's throttled and what's preventing it from not being throttled) and what action may I take or how to unthrottle it? Maybe there is some option to make it less strict or disable it, or maybe decreasing CPU temperature further more may help?
Additional details:
$ uname -a
Darwin MBP.local 15.2.0 Darwin Kernel Version 15.2.0: Fri Nov 13 19:56:56 PST 2015; root:xnu-3248.20.55~2/RELEASE_X86_64 x86_64 i386 MacBookPro11,3 Darwin
$ top | head
Processes: 464 total, 19 running, 8 stuck, 437 sleeping, 4157 threads
2016/05/25 12:31:44
Load Avg: 30.72, 39.86, 29.86
CPU usage: 14.86% user, 46.0% sys, 39.12% idle
SharedLibs: 84M resident, 18M data, 7760K linkedit.
MemRegions: 360850 total, 2901M resident, 55M private, 435M shared.
PhysMem: 16G used (8494M wired), 5664K unused.
VM: 1406G vsize, 528M framework vsize, 3900541086(0) swapins, 3913990343(0) swapouts.
Networks: packets: 136234033/128G in, 133429405/73G out.
Disks: 288046480/15T read, 220716626/15T written.
$ macosver -h | tail -n1
ProductVersion 10.11.2