The documentation was mentioning the "future SCHED EDF" as the solution for fine-grained control of deadline/period. This patch updates this citing the (now) existing SCHED_DEADLINE. Signed-off-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx> Cc: Jonathan Corbet <corbet@xxxxxxx> Cc: Juri Lelli <juri.lelli@xxxxxxxxxx> Cc: Luca Abeni <luca.abeni@xxxxxxxxxxxxxxx> Cc: Tommaso Cucinotta <tommaso.cucinotta@xxxxxxxxxxxxxxx> Cc: Claudio Scordino <claudio@xxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: linux-doc@xxxxxxxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx --- Documentation/scheduler/sched-rt-group.txt | 19 +++++-------------- 1 file changed, 5 insertions(+), 14 deletions(-) diff --git a/Documentation/scheduler/sched-rt-group.txt b/Documentation/scheduler/sched-rt-group.txt index d8fce3e78457..ed763c243914 100644 --- a/Documentation/scheduler/sched-rt-group.txt +++ b/Documentation/scheduler/sched-rt-group.txt @@ -153,7 +153,7 @@ There is work in progress to make the scheduling period for each group The constraint on the period is that a subgroup must have a smaller or equal period to its parent. But realistically its not very useful _yet_ -as its prone to starvation without deadline scheduling. +as its prone to starvation. Consider two sibling groups A and B; both have 50% bandwidth, but A's period is twice the length of B's. @@ -168,16 +168,7 @@ This means that currently a while (1) loop in A will run for the full period of B and can starve B's tasks (assuming they are of lower priority) for a whole period. -The next project will be SCHED_EDF (Earliest Deadline First scheduling) to bring -full deadline scheduling to the linux kernel. Deadline scheduling the above -groups and treating end of the period as a deadline will ensure that they both -get their allocated time. - -Implementing SCHED_EDF might take a while to complete. Priority Inheritance is -the biggest challenge as the current linux PI infrastructure is geared towards -the limited static priority levels 0-99. With deadline scheduling you need to -do deadline inheritance (since priority is inversely proportional to the -deadline delta (deadline - now)). - -This means the whole PI machinery will have to be reworked - and that is one of -the most complex pieces of code we have. +Nowadays it is possible to use the deadline scheduler (SCHED_DEADLINE) to +allocate runtime/period for tasks. The deadline scheduler does not suffer the +side effects explained above. For more information about the deadline +scheduler, you should read Documentation/scheduler/sched-deadline.txt. -- 2.14.3 -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
