Messages in this thread | | | From | Rainer Fiebig <> | Subject | Building kernels under 5.10 takes twice as long as under 4.19 | Date | Thu, 18 Mar 2021 19:42:14 +0100 |
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Hi!
I tried kernel 5.10.x and encountered a strange problem: building the same kernel (5.10.22/23) took roughly twice as long as under 4.19.179.
This is reproducible under kernels 5.9, 5.8 and 5.6. The latter is where it apparently starts, kernel 5.5 is not affected.
Here's an example:
5.6 built under 5.5, -j4 ************************ [...] LD [M] sound/pci/hda/snd-hda-intel.ko
real 11m44,125s user 38m35,022s sys 3m17,940s
5.6 under 5.6, -j4 ****************** [...] LD [M] sound/pci/hda/snd-hda-intel.ko
real 23m25,834s user 26m7,738s sys 2m42,292s
Always after "make mrproper", with -j4, identical .config and everything else unchanged. It's also there with a default .config.
When I build the kernels under 4.19 or 5.5 with -j4, CPU-usage is 100 % almost all the time. Under 5.6 and later, CPU-usage goes down to ~30 % for longer periods during which I see long sections of sorted items like "fs/xfs" which I had never noticed before.
CPUfreq-governor was "ondemand" in all cases (for 5.10 set via commandline). The CPU is an Intel Core i3 (Clarkdale/Ironlake; still fast enough for a snappy LFS-Linux with Plasma 5).
Before writing a bug-report: any ideas what might cause this or how to narrow the search? A full bisect between 5.5 and 5.6 would be a real drag.
And please don't say this is a feature now. ;)
Thanks.
Rainer
-- The truth always turns out to be simpler than you thought. Richard Feynman
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