On Thu, 2016-02-25 at 09:40 +0100, Ingo Molnar wrote: > * Mike Galbraith <umgwanakikbuti@xxxxxxxxx> wrote: > > > On Thu, 2016-02-25 at 09:14 +0100, Ingo Molnar wrote: > > > > > But but ... 'context tracking' is not really something that a regular distro > > > kernel cares about much - it's a nohz-full special AFAICS. > > Let me qualify that: with the timer code maintenance hat on I really love all nohz > variants (the deeper the better), but now I have my x86 maintainer hat on, and as > such I'm really annoyed at those nohz folks adding overhead to the syscall hot > path! ;-) > > > (psst.. distros are shipping it) > > Yeah, indeed, Fedora does - but AFAICS: > > fomalhaut:~> grep NO_HZ /boot/config-4.1.13-100.fc21.x86_64 > CONFIG_NO_HZ_COMMON=y > # CONFIG_NO_HZ_IDLE is not set > CONFIG_NO_HZ_FULL=y > # CONFIG_NO_HZ_FULL_ALL is not set > # CONFIG_NO_HZ_FULL_SYSIDLE is not set > CONFIG_NO_HZ=y > CONFIG_RCU_FAST_NO_HZ=y > > ... which won't result in actual full-nohz CPUs unless you boot it with a special > boot parameter, right? Yeah, you have to manually enable it unless you (in a suicidal moment) enable CONFIG_NO_HZ_FULL_ALL. > What is the easiest way to query which/how many CPUs are in nohz-full mode and do > context tracking? I somehow thought /proc/timer_* had that info, but that does not > appear to be the case. /sys/devices/system/cpu/nohz_full -Mike -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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