Messages in this thread Patch in this message | | | Date | Mon, 22 Feb 2016 16:31:32 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v10 1/3] cpufreq: Add mechanism for registering utilization update callbacks |
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On Mon, Feb 22, 2016 at 03:33:02PM +0100, Vincent Guittot wrote:
> > Right, so I had a wee look at that again, and had a quick chat with Juri > > on IRC. So the main difference seems to be that you guys want to know > > why the utilization changed, as opposed to purely _that_ it changed. > > Yes, the main goal was to be able to filter the useful and useless > update of rq's utilization in order to minimize/optimize the trig of > an update of the frequency. These patches have been made for a cpufreq > driver that reacts far slower than scheduler. It's might worth > starting with a simple solution and update it after
Right, always start simple :-)
> > And hence you have callbacks all over the place. > > > > I'm not too sure I really like that too much, it bloats the code and > > somewhat obfuscates the point. > > > > So I would really like there to be just the one callback when we > > actually compute a new number, and that is update_load_avg(). > > > > Now I think we can 'easily' propagate the information you want into > > update_load_avg() (see below), but I would like to see actual arguments > > for why you would need this. > > Your proposal is interesting except that we are interested in the rq's > utilization more that se's ones so we should better use > update_cfs_rq_load_avg and few additional place like > attach_entity_load_avg which bypasses update_cfs_rq_load_avg to update > rq's utilization and load
Ah, so the intent was to use the rq->cfs util, but I might have gotten a little lost in the load update code (I always get confused by that code if I haven't looked at it for a while).
We can put the hook in update_cfs_rq_load_avg(), that shouldn't be a problem.
--- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2859,29 +2859,6 @@ static inline int update_cfs_rq_load_avg cfs_rq->load_last_update_time_copy = sa->last_update_time; #endif - return decayed || removed; -} - -/* Update task and its cfs_rq load average */ -static inline void update_load_avg(struct sched_entity *se, int update_tg, - enum load_update_type type) -{ - struct cfs_rq *cfs_rq = cfs_rq_of(se); - u64 now = cfs_rq_clock_task(cfs_rq); - struct rq *rq = rq_of(cfs_rq); - int cpu = cpu_of(rq); - - /* - * Track task load average for carrying it to new CPU after migrated, and - * track group sched_entity load average for task_h_load calc in migration - */ - __update_load_avg(now, cpu, &se->avg, - se->on_rq * scale_load_down(se->load.weight), - cfs_rq->curr == se, NULL); - - if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg) - update_tg_load_avg(cfs_rq, 0); - if (cpu == smp_processor_id() && &rq->cfs == cfs_rq) { unsigned long max = rq->cpu_capacity_orig; @@ -2904,6 +2881,29 @@ static inline void update_load_avg(struc cpufreq_update_util(rq_clock(rq), min(cfs_rq->avg.util_avg, max), max); } + + return decayed || removed; +} + +/* Update task and its cfs_rq load average */ +static inline void update_load_avg(struct sched_entity *se, int update_tg, + enum load_update_type type) +{ + struct cfs_rq *cfs_rq = cfs_rq_of(se); + u64 now = cfs_rq_clock_task(cfs_rq); + struct rq *rq = rq_of(cfs_rq); + int cpu = cpu_of(rq); + + /* + * Track task load average for carrying it to new CPU after migrated, and + * track group sched_entity load average for task_h_load calc in migration + */ + __update_load_avg(now, cpu, &se->avg, + se->on_rq * scale_load_down(se->load.weight), + cfs_rq->curr == se, NULL); + + if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg) + update_tg_load_avg(cfs_rq, 0); } static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
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