Painfully slow compilation (read: "make buildworld buildkernel") on not-so-weak system

Lev Serebryakov lev at
Sat Dec 8 11:13:07 UTC 2018

Hello Freebsd-hackers,

 I'm experiencing very strange situation on my lab system which is
E3-1220v2, 8GiB of RAM and 850 EVO SATA SSD (with single ZFS pool).

 It runs CURRENT r341157. Kernel is built *without* INVARIANTS and other
heavy debug aids.

 Everything works great — but compilation. "make -j *1* buildkernel" takes
forever and each compiler invocation takes up to 10 seconds. For example,
I've clocked compilation of sys/dev/aic7xxx/aic7xxx_93cx6.c by stopwatch and
it takes 9 seconds. Please note, it is SINGLE JOB build. If I run "make
-j4" it will be much longer for each compiler out of 4. And all this time
"cc" / "c++" consume 100% of CPU.

 Even when build is single-job, system becomes unresponsive. With
4-job build running it could takes up to minute to switch screen's windows!

 Another strange thing I noticed: when system is in such state, "top -SH"
shows that sometimes very low-profile processes, like clock software
interrupt (!) could consume large amount of CPU for short periods time. When
system is idle there never will be "intr{swi4: clock (0)}" consuming 55% CPU
for one "frame" or sshd, or screen itself.

 I'm completely lost. Is it problem of software? Hardware? If it is
hardware problem what should I blame?

 I've checked all "standard" places — CPU is not throttling, SSD looks
perfectly Ok according to SMART and there is no complains from AHCI driver
about timeouts and such, system doesn't start to use swap.

Best regards,
 Lev                          mailto:lev at

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