Linux package managers are slow

published 2019-08-17 in tags distri debian
Table of contents

I measured how long the most popular Linux distribution’s package manager take to install small and large packages (the ack(1p) source code search Perl script and qemu, respectively).

Where required, my measurements include metadata updates such as transferring an up-to-date package list. For me, requiring a metadata update is the more common case, particularly on live systems or within Docker containers.

All measurements were taken on an Intel(R) Core(TM) i9-9900K CPU @ 3.60GHz running Docker 1.13.1 on Linux 4.19, backed by a Samsung 970 Pro NVMe drive boasting many hundreds of MB/s write performance.

See Appendix B for details on the measurement method and command outputs.

Measurements

Keep in mind that these are one-time measurements. They should be indicative of actual performance, but your experience may vary.

ack (small Perl program)

distribution package manager data wall-clock time rate
Fedora dnf 107 MB 29s 3.7 MB/s
NixOS Nix 15 MB 14s 1.1 MB/s
Debian apt 15 MB 4s 3.7 MB/s
Arch Linux pacman 6.5 MB 3s 2.1 MB/s
Alpine apk 10 MB 1s 10.0 MB/s

qemu (large C program)

distribution package manager data wall-clock time rate
Fedora dnf 266 MB 1m8s 3.9 MB/s
Arch Linux pacman 124 MB 1m2s 2.0 MB/s
Debian apt 159 MB 51s 3.1 MB/s
NixOS Nix 262 MB 38s 6.8 MB/s
Alpine apk 26 MB 2.4s 10.8 MB/s


The difference between the slowest and fastest package managers is 30x!

How can Alpine’s apk and Arch Linux’s pacman be an order of magnitude faster than the rest? They are doing a lot less than the others, and more efficiently, too.

Pain point: too much metadata

For example, Fedora transfers a lot more data than others because its main package list is 60 MB (compressed!) alone. Compare that with Alpine’s 734 KB APKINDEX.tar.gz.

Of course the extra metadata which Fedora provides helps some use case, otherwise they hopefully would have removed it altogether. The amount of metadata seems excessive for the use case of installing a single package, which I consider the main use-case of an interactive package manager.

I expect any modern Linux distribution to only transfer absolutely required data to complete my task.

Pain point: no concurrency

Because they need to sequence executing arbitrary package maintainer-provided code (hooks and triggers), all tested package managers need to install packages sequentially (one after the other) instead of concurrently (all at the same time).

In my blog post “Can we do without hooks and triggers?”, I outline that hooks and triggers are not strictly necessary to build a working Linux distribution.

Thought experiment: further speed-ups

Strictly speaking, the only required feature of a package manager is to make available the package contents so that the package can be used: a program can be started, a kernel module can be loaded, etc.

By only implementing what’s needed for this feature, and nothing more, a package manager could likely beat apk’s performance. It could, for example:

  • skip archive extraction by mounting file system images (like AppImage or snappy)
  • use compression which is light on CPU, as networks are fast (like apk)
  • skip fsync when it is safe to do so, i.e.:
    • package installations don’t modify system state
    • atomic package installation (e.g. an append-only package store)
    • automatically clean up the package store after crashes

Current landscape

Here’s a table outlining how the various package managers listed on Wikipedia’s list of software package management systems fare:

name scope package file format hooks/triggers
AppImage apps image: ISO9660, SquashFS no
snappy apps image: SquashFS yes: hooks
FlatPak apps archive: OSTree no
0install apps archive: tar.bz2 no
nix, guix distro archive: nar.{bz2,xz} activation script
dpkg distro archive: tar.{gz,xz,bz2} in ar(1) yes
rpm distro archive: cpio.{bz2,lz,xz} scriptlets
pacman distro archive: tar.xz install
slackware distro archive: tar.{gz,xz} yes: doinst.sh
apk distro archive: tar.gz yes: .post-install
Entropy distro archive: tar.bz2 yes
ipkg, opkg distro archive: tar{,.gz} yes

Conclusion

As per the current landscape, there is no distribution-scoped package manager which uses images and leaves out hooks and triggers, not even in smaller Linux distributions.

I think that space is really interesting, as it uses a minimal design to achieve significant real-world speed-ups.

I have explored this idea in much more detail, and am happy to talk more about it in my post “Introducing the distri research linux distribution".

There are a couple of recent developments going into the same direction:

Appendix B: measurement details

ack

You can expand each of these:

Fedora’s dnf takes almost 30 seconds to fetch and unpack 107 MB.

% docker run -t -i fedora /bin/bash
[[email protected] /]# time dnf install -y ack
Fedora Modular 30 - x86_64            4.4 MB/s | 2.7 MB     00:00
Fedora Modular 30 - x86_64 - Updates  3.7 MB/s | 2.4 MB     00:00
Fedora 30 - x86_64 - Updates           17 MB/s |  19 MB     00:01
Fedora 30 - x86_64                     31 MB/s |  70 MB     00:02
[…]
Install  44 Packages

Total download size: 13 M
Installed size: 42 M
[…]
real	0m29.498s
user	0m22.954s
sys	0m1.085s

NixOS’s Nix takes 14s to fetch and unpack 15 MB.

% docker run -t -i nixos/nix
39e9186422ba:/# time sh -c 'nix-channel --update && nix-env -i perl5.28.2-ack-2.28'
unpacking channels...
created 2 symlinks in user environment
installing 'perl5.28.2-ack-2.28'
these paths will be fetched (14.91 MiB download, 80.83 MiB unpacked):
  /nix/store/57iv2vch31v8plcjrk97lcw1zbwb2n9r-perl-5.28.2
  /nix/store/89gi8cbp8l5sf0m8pgynp2mh1c6pk1gk-attr-2.4.48
  /nix/store/gkrpl3k6s43fkg71n0269yq3p1f0al88-perl5.28.2-ack-2.28-man
  /nix/store/iykxb0bmfjmi7s53kfg6pjbfpd8jmza6-glibc-2.27
  /nix/store/k8lhqzpaaymshchz8ky3z4653h4kln9d-coreutils-8.31
  /nix/store/svgkibi7105pm151prywndsgvmc4qvzs-acl-2.2.53
  /nix/store/x4knf14z1p0ci72gl314i7vza93iy7yc-perl5.28.2-File-Next-1.16
  /nix/store/zfj7ria2kwqzqj9dh91kj9kwsynxdfk0-perl5.28.2-ack-2.28
copying path '/nix/store/gkrpl3k6s43fkg71n0269yq3p1f0al88-perl5.28.2-ack-2.28-man' from 'https://cache.nixos.org'...
copying path '/nix/store/iykxb0bmfjmi7s53kfg6pjbfpd8jmza6-glibc-2.27' from 'https://cache.nixos.org'...
copying path '/nix/store/x4knf14z1p0ci72gl314i7vza93iy7yc-perl5.28.2-File-Next-1.16' from 'https://cache.nixos.org'...
copying path '/nix/store/89gi8cbp8l5sf0m8pgynp2mh1c6pk1gk-attr-2.4.48' from 'https://cache.nixos.org'...
copying path '/nix/store/svgkibi7105pm151prywndsgvmc4qvzs-acl-2.2.53' from 'https://cache.nixos.org'...
copying path '/nix/store/k8lhqzpaaymshchz8ky3z4653h4kln9d-coreutils-8.31' from 'https://cache.nixos.org'...
copying path '/nix/store/57iv2vch31v8plcjrk97lcw1zbwb2n9r-perl-5.28.2' from 'https://cache.nixos.org'...
copying path '/nix/store/zfj7ria2kwqzqj9dh91kj9kwsynxdfk0-perl5.28.2-ack-2.28' from 'https://cache.nixos.org'...
building '/nix/store/q3243sjg91x1m8ipl0sj5gjzpnbgxrqw-user-environment.drv'...
created 56 symlinks in user environment
real	0m 14.02s
user	0m 8.83s
sys	0m 2.69s

Debian’s apt takes almost 10 seconds to fetch and unpack 16 MB.

% docker run -t -i debian:sid
[email protected]:/# time (apt update && apt install -y ack-grep)
Get:1 http://cdn-fastly.deb.debian.org/debian sid InRelease [233 kB]
Get:2 http://cdn-fastly.deb.debian.org/debian sid/main amd64 Packages [8270 kB]
Fetched 8502 kB in 2s (4764 kB/s)
[…]
The following NEW packages will be installed:
  ack ack-grep libfile-next-perl libgdbm-compat4 libgdbm5 libperl5.26 netbase perl perl-modules-5.26
The following packages will be upgraded:
  perl-base
1 upgraded, 9 newly installed, 0 to remove and 60 not upgraded.
Need to get 8238 kB of archives.
After this operation, 42.3 MB of additional disk space will be used.
[…]
real	0m9.096s
user	0m2.616s
sys	0m0.441s

Arch Linux’s pacman takes a little over 3s to fetch and unpack 6.5 MB.

% docker run -t -i archlinux/base
[[email protected] /]# time (pacman -Sy && pacman -S --noconfirm ack)
:: Synchronizing package databases...
 core            132.2 KiB  1033K/s 00:00
 extra          1629.6 KiB  2.95M/s 00:01
 community         4.9 MiB  5.75M/s 00:01
[…]
Total Download Size:   0.07 MiB
Total Installed Size:  0.19 MiB
[…]
real	0m3.354s
user	0m0.224s
sys	0m0.049s

Alpine’s apk takes only about 1 second to fetch and unpack 10 MB.

% docker run -t -i alpine
/ # time apk add ack
fetch http://dl-cdn.alpinelinux.org/alpine/v3.10/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.10/community/x86_64/APKINDEX.tar.gz
(1/4) Installing perl-file-next (1.16-r0)
(2/4) Installing libbz2 (1.0.6-r7)
(3/4) Installing perl (5.28.2-r1)
(4/4) Installing ack (3.0.0-r0)
Executing busybox-1.30.1-r2.trigger
OK: 44 MiB in 18 packages
real	0m 0.96s
user	0m 0.25s
sys	0m 0.07s

qemu

You can expand each of these:

Fedora’s dnf takes over a minute to fetch and unpack 266 MB.

% docker run -t -i fedora /bin/bash
[[email protected] /]# time dnf install -y qemu
Fedora Modular 30 - x86_64            3.1 MB/s | 2.7 MB     00:00
Fedora Modular 30 - x86_64 - Updates  2.7 MB/s | 2.4 MB     00:00
Fedora 30 - x86_64 - Updates           20 MB/s |  19 MB     00:00
Fedora 30 - x86_64                     31 MB/s |  70 MB     00:02
[…]
Install  262 Packages
Upgrade    4 Packages

Total download size: 172 M
[…]
real	1m7.877s
user	0m44.237s
sys	0m3.258s

NixOS’s Nix takes 38s to fetch and unpack 262 MB.

% docker run -t -i nixos/nix
39e9186422ba:/# time sh -c 'nix-channel --update && nix-env -i qemu-4.0.0'
unpacking channels...
created 2 symlinks in user environment
installing 'qemu-4.0.0'
these paths will be fetched (262.18 MiB download, 1364.54 MiB unpacked):
[…]
real	0m 38.49s
user	0m 26.52s
sys	0m 4.43s

Debian’s apt takes 51 seconds to fetch and unpack 159 MB.

% docker run -t -i debian:sid
[email protected]:/# time (apt update && apt install -y qemu-system-x86)
Get:1 http://cdn-fastly.deb.debian.org/debian sid InRelease [149 kB]
Get:2 http://cdn-fastly.deb.debian.org/debian sid/main amd64 Packages [8426 kB]
Fetched 8574 kB in 1s (6716 kB/s)
[…]
Fetched 151 MB in 2s (64.6 MB/s)
[…]
real	0m51.583s
user	0m15.671s
sys	0m3.732s

Arch Linux’s pacman takes 1m2s to fetch and unpack 124 MB.

% docker run -t -i archlinux/base
[[email protected] /]# time (pacman -Sy && pacman -S --noconfirm qemu)
:: Synchronizing package databases...
 core       132.2 KiB   751K/s 00:00
 extra     1629.6 KiB  3.04M/s 00:01
 community    4.9 MiB  6.16M/s 00:01
[…]
Total Download Size:   123.20 MiB
Total Installed Size:  587.84 MiB
[…]
real	1m2.475s
user	0m9.272s
sys	0m2.458s

Alpine’s apk takes only about 2.4 seconds to fetch and unpack 26 MB.

% docker run -t -i alpine
/ # time apk add qemu-system-x86_64
fetch http://dl-cdn.alpinelinux.org/alpine/v3.10/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.10/community/x86_64/APKINDEX.tar.gz
[…]
OK: 78 MiB in 95 packages
real	0m 2.43s
user	0m 0.46s
sys	0m 0.09s