Current RTDS scheduler is time driven and is called every 1ms. During each scheduler call, the repl_update() scans both runq and depeletedq, which might not be necessary every 1ms.
Since each vcpu is implemented as a deferable server, budget is preserved during its period and refilled in the next. It is not necessary to check every 1ms as the current design does. The replenishment is needed at the nearest next period(nearest current_deadline) of all runnable vcpus. This improved design tries to reduce scheduler invocation by using an event driven approach;rt_schedule() will return a value when the scheduler needs to be called next time. In addition, the sched_rt will have one dedicated timer to handle replenishment when necessary. In other words, the budget replenishment and scheduler decision(rt_schedule) are separated. The transient behavior should be noted. It happens between a vcpu tickles and a pcpu actually picks it. As previous discussions, this is unavoidable. Previous discussions: http://lists.xenproject.org/archives/html/xen-devel/2015-06/msg02629.html Signed-off-by: Tianyang Chen <ti...@seas.upenn.edu> Signed-off-by: Meng Xu <men...@cis.upenn.edu> Signed-off-by: Dagaen Golomb <dgol...@seas.upenn.edu> Tianyang Chen (1): xen: sched: convert RTDS from time to event driven model xen/common/sched_rt.c | 291 ++++++++++++++++++++++++++++++++++++------------- 1 file changed, 213 insertions(+), 78 deletions(-) -- 1.7.9.5 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
