Messages in this thread | | | From | Linus Torvalds <> | Date | Fri, 12 Jan 2024 12:30:18 -0800 | Subject | Re: [GIT PULL] Scheduler changes for v6.8 |
| |
Ok, so testing a bit more. On a working kernel, when I do an empty "make" (which is the fast test I've used), it's all single-threaded because it's just 'make' doing tons of stat calls and string operations.
And "cat /proc/cpuinfo | grep MHz" shows a nice clear signal:
... cpu MHz : 2200.000 cpu MHz : 2200.000 cpu MHz : 4425.339 cpu MHz : 2200.000 ...
so it boosts up to the top boost frequency.
Without the revert, doing the same thing, what I see is very different. It's all just
... cpu MHz : 2200.000 cpu MHz : 2200.000 cpu MHz : 2200.000 cpu MHz : 2200.000 ...
which certainly explains why it takes 45s rather than 22s to do a full empty build.
Btw, the "full empty build" I do is literally just
timestamp sh -c "make -j128 > ../makes"
where 'timestamp' is my stupid little wrapper program that just shows elapsed time as the command is progressing (as opposed to "time", which just shows it at the end).
Side note: that 4425.339 is very much the boost frequency, 'cpupower' reports
$ cpupower frequency-info analyzing CPU 0: driver: acpi-cpufreq CPUs which run at the same hardware frequency: 0 CPUs which need to have their frequency coordinated by software: 0 maximum transition latency: Cannot determine or is not supported. hardware limits: 2.20 GHz - 3.70 GHz available frequency steps: 3.70 GHz, 2.80 GHz, 2.20 GHz available cpufreq governors: conservative ondemand userspace powersave performance schedutil current policy: frequency should be within 2.20 GHz and 3.70 GHz. The governor "schedutil" may decide which speed to use within this range. current CPU frequency: Unable to call hardware current CPU frequency: 2.20 GHz (asserted by call to kernel) boost state support: Supported: yes Active: no
and for all I know the scheduler got confused by the fact that it thinks the hardware limits are 2.2-3.7 GHz. But the 3970X has a boost frequency of 4.5GHz, and yes, I very much want it.
I will test Vincent's test-patch next.
Linus
| |