Linux Kernel 5.5.0 commit 0ddad21d3e99

[PhysixProject]

Describe the bug
Observed on a lfs linux distro:
Compiled the kernel (with gcc 9.2) at commit id 0ddad21d3e99 (version5.5).
After booting this new kernel, and executing make -j8 on the linux src,
the 8 core system load reported by uptime never hits above ~1.68.

Could not reproduce this on Debian 10.2, (same kernel config, used gcc 8.3).

Next: Test debian against gcc 9.2 exact config as physix

[PhysixProject]

From commit description

[ Note! This kernel improvement seems to be very good at triggering a
race condition in the make jobserver (in GNU make 4.2.1) for me. It's
a long known bug that was fixed back in June 2017 by GNU make commit
b552b0525198 ("[SV 51159] Use a non-blocking read with pselect to
avoid hangs.").

  But there wasn't a new release of GNU make until 4.3 on Jan 19 2020,
  so a number of distributions may still have the buggy version. Some
  have backported the fix to their 4.2.1 release, though, and even
  without the fix it's quite timing-dependent whether the bug actually
  is hit. ]

will update make package

[PhysixProject]

Confirmed.
Upgrade to make 4.3 resolve this issue