Help¶

When selected, the scheduler ready queue will be implemented
as the classic/textbook array of lists, one per priority
(max 32 priorities).  This corresponds to the scheduler
algorithm used in Zephyr versions prior to 1.12.  It incurs
only a tiny code size overhead vs. the "dumb" scheduler and
runs in O(1) time in almost all circumstances with very low
constant factor.  But it requires a fairly large RAM budget
to store those list heads, and the limited features make it
incompatible with features like deadline scheduling that
need to sort threads more finely, and SMP affinity which
need to traverse the list of threads.  Typical applications
with small numbers of runnable threads probably want the
DUMB scheduler.

Direct dependencies¶

!SCHED_DEADLINE && <choice SCHED_ALGORITHM: Scheduler priority queue algorithm>

(Includes any dependencies from ifs and menus.)

Kconfig definition¶

At <Zephyr>/kernel/Kconfig:245

Included via <Zephyr>/Kconfig:8 → <Zephyr>/Kconfig.zephyr:30

Menu path: (Top) → General Kernel Options → Scheduler priority queue algorithm

config SCHED_MULTIQ
    bool "Traditional multi-queue ready queue"
    depends on !SCHED_DEADLINE && <choice SCHED_ALGORITHM>
    help
      When selected, the scheduler ready queue will be implemented
      as the classic/textbook array of lists, one per priority
      (max 32 priorities).  This corresponds to the scheduler
      algorithm used in Zephyr versions prior to 1.12.  It incurs
      only a tiny code size overhead vs. the "dumb" scheduler and
      runs in O(1) time in almost all circumstances with very low
      constant factor.  But it requires a fairly large RAM budget
      to store those list heads, and the limited features make it
      incompatible with features like deadline scheduling that
      need to sort threads more finely, and SMP affinity which
      need to traverse the list of threads.  Typical applications
      with small numbers of runnable threads probably want the
      DUMB scheduler.

(The ‘depends on’ condition includes propagated dependencies from ifs and menus.)