Bug#1119299: cupsd has around 0.5-1% permanent CPU usage

[Till Kamppeter <till.kamppeter@gmail.com>]

On 10/28/25 21:50, Ralf Jung wrote:
> Package: cups
> Version: 2.4.14-1
> Severity: normal
>
> Dear Maintainer,
>
> since the most recent update, I regularly see cups show up in htop when I sort
> processes by CPU usage: around half the time, when the system is idle, I see
> cups among the top 5 processes by CPU consumption. This is on a full GNOME
> desktop system, with multiple chat applications, browsers, and IDEs all running
> at the same time -- and yet cupsd manages to show up among those other,
> typically much more resource-demanding processes. This is while cups should be
> entirely idle, no local printer is even connected, and the two configured
> network printers are not reachable either. There are no jobs in any queue.
>
> I restarted cupsd to see if this persists, and it did: after around 4 minutes,
> cups accumulated around 2s of CPU usage. That's not much, of course, but cups
> does stand out in the process list sorted by total CPU time since it is
> constantly moving upwards even though it shouldn't be doing anything.
>
> I did not see this before a recent big 'apt upgrade'.
>
> I could imagine that this is caused by some other application constantly trying
> to talk to cups for no good reason, but I am not sure how I would go about
> tracing that to its origin, so I am reporting the bug where I see the symptoms.

Could you set the log level of CUPS to debug mode:

$ cupsctl --debug-logging

More verbose:

$ cupsctl LogLevel=debug2

to see what could be hammering on CUPS.

Could you also try to turn off/disconnect Wi-Fi, Ethernet, D-Bus (one of these 
at a time) and see whether the load goes away? This way one can find out through 
which communication channel cupsd gets hammered.

With the commands

$ ippfind

and

$ driverless
You find IPP print destinations in your local network.

They can also cause load on cupsd. By turning off devices (computers, printers) 
which provide an IPP print destination you can find out which device is the culprit.

   Till

> Kind regards,
> Ralf
>
> -- System Information:
> Debian Release: forky/sid
>    APT prefers testing-debug
>    APT policy: (500, 'testing-debug'), (500, 'testing')
> Architecture: amd64 (x86_64)
> Foreign Architectures: i386
>
> Kernel: Linux 6.16.12+deb14+1-amd64 (SMP w/20 CPU threads; PREEMPT)
> Kernel taint flags: TAINT_CPU_OUT_OF_SPEC
> Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US:en
> Shell: /bin/sh linked to /usr/bin/dash
> Init: systemd (via /run/systemd/system)
> LSM: AppArmor: enabled
>
> Versions of packages cups depends on:
> ii  cups-client            2.4.14-1
> ii  cups-common            2.4.14-1
> ii  cups-core-drivers      2.4.14-1
> ii  cups-daemon            2.4.14-1
> ii  cups-filters           1.28.17-6
> ii  cups-ppdc              2.4.14-1
> ii  cups-server-common     2.4.14-1
> ii  debconf [debconf-2.0]  1.5.91
> ii  ghostscript            10.05.1~dfsg-3
> ii  libavahi-client3       0.8-17
> ii  libavahi-common3       0.8-17
> ii  libc6                  2.41-12
> ii  libcups2t64            2.4.14-1
> ii  libgcc-s1              15.2.0-4
> ii  libstdc++6             15.2.0-4
> ii  libusb-1.0-0           2:1.0.29-2
> ii  poppler-utils          25.03.0-11.1
> ii  procps                 2:4.0.4-9
>
> Versions of packages cups recommends:
> ii  avahi-daemon  0.8-17
> ii  colord        1.4.8-1
>
> Versions of packages cups suggests:
> pn  cups-bsd                                   <none>
> pn  cups-pdf                                   <none>
> pn  foomatic-db-compressed-ppds | foomatic-db  <none>
> ii  smbclient                                  2:4.23.2+dfsg-1
> ii  udev                                       258.1-1
>
> -- debconf information:
>    cupsys/backend: lpd, socket, usb, snmp, dnssd
>    cupsys/raw-print: true