Hi Joonsoo,
>>> I think that it is real problem that sysctl_sched_min_granularity is not >>> guaranteed for each task. >>> Instead of this patch, how about considering low bound? >>> >>> if (slice < sysctl_sched_min_granularity) >>> slice = sysctl_sched_min_granularity; >> >> Consider the below scenario. >> >> A runqueue has two task groups,each with 10 tasks. >> >> With the current implementation,each of these tasks get a sched_slice of >> 2ms.Hence in a matter of (10*2) + (10*2) = 40 ms, all tasks( all tasks >> of both the task groups) will get the chance to run. >> >> But what is the scheduling period in this scenario? Is it 40ms (extended >> sysctl_sched_latency), which is the scheduling period for each of the >> runqueues with 10 tasks in it? >> Or is it 80ms which is the total of the scheduling periods of each of >> the run queues with 10 tasks.Either way all tasks seem to get scheduled >> atleast once within the scheduling period.So we appear to be safe. >> Although the sched_slice < sched_min_granularity. >> >> With your above lower bound of sysctl_sched_min_granularity, each task >> of each tg gets 4ms as its sched_slice.So in a matter of >> (10*4) + (10*4) = 80ms,all tasks get to run. With the above question >> being put forth here as well, we don't appear to be safe if the >> scheduling_period is considered to be 40ms, otherwise it appears fine to >> me, because it ensures the sched_slice is atleast sched_min_granularity >> no matter what. > > So, you mean that we should guarantee to schedule each task atleast once > in sysctl_sched_latency? I would rather say all tasks get to run atleast once in a sched_period, which could be just sysctl_sched_latency or more depending on the number of tasks in the current implementation. But this is not guaranteed in current code, > this is why I made this patch. Please refer a patch description. Ok,take the example of a runqueue with 2 task groups,each with 10 tasks.Same as your previous example. Can you explain how your patch ensures that all 20 tasks get to run atleast once in a sched_period? Regards Preeti U Murthy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
