Hi Daniel, On 01/02/18 11:31, Daniel Bristot de Oliveira wrote: > 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. True. But it doesn't have support for groups yet (while this doc seems to refer to groups). Maybe add a paragraph about this? Thanks, - Juri -- 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
