1 ===============
2 EEVDF Scheduler
3 ===============
4
5 The "Earliest Eligible Virtual Deadline First"
6 in a scientific publication in 1995 [1]. The L
7 transitioning to EEVDF in version 6.6 (as a ne
8 away from the earlier Completely Fair Schedule
9 of EEVDF proposed by Peter Zijlstra in 2023 [2
10 regarding CFS can be found in
11 Documentation/scheduler/sched-design-CFS.rst.
12
13 Similarly to CFS, EEVDF aims to distribute CPU
14 runnable tasks with the same priority. To do s
15 time to each task, creating a "lag" value that
16 whether a task has received its fair share of
17 with a positive lag is owed CPU time, while a
18 has exceeded its portion. EEVDF picks tasks wi
19 zero and calculates a virtual deadline (VD) fo
20 with the earliest VD to execute next. It's imp
21 allows latency-sensitive tasks with shorter ti
22 which helps with their responsiveness.
23
24 There are ongoing discussions on how to manage
25 tasks; but at the time of writing EEVDF uses a
26 on virtual run time (VRT). This prevents tasks
27 by sleeping briefly to reset their negative la
28 remains on the run queue but marked for "defer
29 lag to decay over VRT. Hence, long-sleeping ta
30 reset. Finally, tasks can preempt others if th
31 can request specific time slices using the new
32 which further facilitates the job of latency-s
33
34 REFERENCES
35 ==========
36
37 [1] https://citeseerx.ist.psu.edu/document?rep
38
39 [2] https://lore.kernel.org/lkml/a79014e6-ea83
40
41 [3] https://lwn.net/Articles/969062/
42
43 [4] https://lwn.net/Articles/925371/
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