Realtime kernel and multipathd priority

Bug #1997361 reported by Guillaume Beuzeboc
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
ubuntu-realtime
Triaged
Wishlist
Unassigned

Bug Description

Ubuntu realtime kernel seems to be meant to run on an Ubuntu-server distro.

The default Ubuntu-server install (20.04, 22.04) comes (in minimal setup) with multipathd (from the multipath-tools package).

Multipathd has a priority of 99 (RT). The highest priority possible.
https://github.com/opensvc/multipath-tools/blob/3db6872d9a418261b02be4755258a9928b6bb7ac/multipathd/main.c#L3106

It will make the realtime process of a user not a priority compared to multipathd.
Enabling Ubuntu realtime kernel could maybe warn about the Multipathd process that make sens on a server but probably not on a realtime system.

Revision history for this message
Joseph Salisbury (jsalisbury) wrote :

If using multipathd with real-time, it is probably best to use cpu/core affinity for the multipathd daemon and bind real-time processes to other cpus/cores.

A message of multipathd having a priority of 99 would be helpful. Maybe a message of the day or something similar, that reports the current priority of all system daemons? That would help when initially setting up a real-time system.

Changed in ubuntu-realtime:
importance: Undecided → Medium
status: New → Triaged
Changed in ubuntu-realtime:
importance: Medium → Wishlist
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