[Pkg-zfsonlinux-devel] Bug#951079: zfs-dkms: Uses only single core during compile

[Witold Baryluk]

Package: zfs-dkms
Version: 0.8.3-1
Severity: normal

This is actually for zfs-dkms 0.8.2-3~bpo10+1 from buster-backports, but
I am filling this bug on another computer running sid.

During zfs-dkms post-install, it build modules for all installed kernels,
I did notice it is very slow, and looking at the top, it looks to be
using just a single core during a build process.

Manually building zfs from source with make -j8 was significantly faster.

The machine I was doing this on has 8 cores (AMD FX-8320). On more modern
machines (like Ryzen 3950, or 2950X, difference could be more dramatic).

I have no idea if this is the issue with zfs-dkms or dkms in general, but
compiling using single process only isn't the best idea. Use all (or half
maybe?) available cores if possible, and limit the impact to the rest of
the system using schedtool or nice. The apt install / dpkg itself will
impact the CPU usage anyway, so it is totally expected for the CPU usage
to be high during this process. So I see no reason to not use all
available core and speed up the install / upgrade.


Cheers,
Witold






-- System Information:
Debian Release: bullseye/sid
  APT prefers testing-debug
  APT policy: (500, 'testing-debug'), (500, 'unstable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 5.2.0-3-amd64 (SMP w/32 CPU cores)
Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages zfs-dkms depends on:
ii  debconf [debconf-2.0]  1.5.73
ii  dkms                   2.8.1-5
ii  file                   1:5.38-4
ii  libc6-dev [libc-dev]   2.29-10
ii  libpython3-stdlib      3.7.5-3
ii  lsb-release            11.1.0
ii  perl                   5.30.0-9
ii  python3-distutils      3.8.0-1

Versions of packages zfs-dkms recommends:
ii  linux-libc-dev  5.4.13-1
ii  zfs-zed         0.8.3-1
ii  zfsutils-linux  0.8.3-1

Versions of packages zfs-dkms suggests:
pn  debhelper  <none>

-- debconf information excluded