Thanks, Ben, On Mon, Jul 07, 2014 at 03:25:07PM -0700, bseg...@google.com wrote: > > Yeah, while this is technically limited to 1/us (per cpu), it is still > much higher - the replaced code would do updates generally only on > period overflow (1ms) and even then only with nontrivial delta. >
Will update it in "batch" mode as I replied to Peter. Whether or not set up a threshold to not update trivial delta, will see. > Also something to note is that cfs_rq->load_avg just takes samples of > load.weight every 1us, which seems unfortunate. We thought this was ok > for p->se.load.weight, because it isn't really likely for userspace to > be calling nice(2) all the time, but wake/sleeps are more frequent, > particularly on newer cpus. Still, it might not be /that/ bad. The sampling of cfs_rq->load.weight should be equivalent to the current code in that at the end of day cfs_rq->load.weight worth of runnable would contribute to runnable_load_avg/blocked_load_avg for both the current and the rewrite. > Also, as a nitpick/annoyance this does a lot of > if (entity_is_task(se)) __update_load_avg(... se ...) > __update_load_avg(... cfs_rq_of(se) ...) > which is just a waste of the avg struct on every group se, and all it > buys you is the ability to not have a separate rq->avg struct (removed > by patch 1) instead of rq->cfs.avg. I actually struggled on this issue. As we only need a sched_avg for task (not entity), and a sched_avg for cfs_rq, I planned to move entity avg to task. Good? So left are the migrate_task_rq_fair() not holding lock issue and cfs_rq->avg.load_avg overflow issue. I need some time to study them. Overall, I think none of these issues are originally caused by combination/split of runnable and blocked. It is just a matter of how synchronized we want to be (this rewrite is the most synchronized), and the workaround I need to borrow from the current codes. Yuyang -- 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/
