Messages in this thread Patch in this message | | | Date | Tue, 21 Feb 2006 17:21:47 +1100 | From | Peter Williams <> | Subject | Re: [PATCH] sched: Consolidated and improved smpnice patch |
| |
Con Kolivas wrote: > On Tuesday 21 February 2006 09:35, Peter Williams wrote: > >>Con Kolivas wrote: >> >>>On Monday 20 February 2006 16:02, Peter Williams wrote: >>>[snip description] >>> >>>Hi peter, I've had a good look and have just a couple of comments: >>> >>>--- >>> #endif >>> int prio, static_prio; >>>+#ifdef CONFIG_SMP >>>+ int load_weight; /* for load balancing purposes */ >>>+#endif >>>--- >>> >>>Can this be moved up to be part of the other ifdef CONFIG_SMP? Not highly >>>significant since it's in a .h file but looks a tiny bit nicer. >> >>I originally put it where it is to be near prio and static_prio which >>are referenced at the same time as it BUT that doesn't happen often >>enough to justify it anymore so I guess it can be moved. > > > Well it is just before prio instead of just after it now and I understand the > legacy of the position. > > >>>--- >>>+/* >>>+ * Priority weight for load balancing ranges from 1/20 (nice==19) to >>>459/20 (RT >>>+ * priority of 100). >>>+ */ >>>+#define NICE_TO_LOAD_PRIO(nice) \ >>>+ ((nice >= 0) ? (20 - (nice)) : (20 + (nice) * (nice))) >>>+#define LOAD_WEIGHT(lp) \ >>>+ (((lp) * SCHED_LOAD_SCALE) / NICE_TO_LOAD_PRIO(0)) >>>+#define NICE_TO_LOAD_WEIGHT(nice) >>>LOAD_WEIGHT(NICE_TO_LOAD_PRIO(nice)) +#define PRIO_TO_LOAD_WEIGHT(prio) >>>NICE_TO_LOAD_WEIGHT(PRIO_TO_NICE(prio)) >>>+#define RTPRIO_TO_LOAD_WEIGHT(rp) \ >>>+ LOAD_WEIGHT(NICE_TO_LOAD_PRIO(-20) + (rp)) >>>--- >>> >>>The weighting seems not related to anything in particular apart from >>>saying that -nice values are more heavily weighted. >> >>The idea (for the change from the earlier model) was to actually give >>equal weight to negative and positive nices. Under the old (purely >>linear) model a nice=19 task has 1/20th the weight of a nice==0 task but >>a nice==-20 task only has twice the weight of a nice==0 so that system >>is heavily weighted against negative nices. With this new mapping a >>nice=19 has 1/20th and a nice==-19 has 20 times the weight of a nice==0 >>task and to me that is symmetric. Does that make sense to you? > > > Yes but what I meant is it's still an arbitrary algorithm which is why I > suggested proportional to tasks' timeslice because then it should scale with > the theoretically allocated cpu resource. > > >>Should I add a comment to explain the mapping? >> >> >>>Since you only do this when >>>setting the priority of tasks can you link it to the scale of >>>(SCHED_NORMAL) tasks' timeslice instead even though that will take a >>>fraction more calculation? RTPRIO_TO_LOAD_WEIGHT is fine since there >>>isn't any obvious cpu proportion relationship to rt_prio level. >> >>Interesting idea. I'll look at this more closely. > > > Would be just a matter of using task_timeslice(p) and making it proportional > to some baseline ensuring the baseline works at any HZ.
How does the attached patch grab you? It's independent of HZ.
Peter -- Peter Williams pwil3058@bigpond.net.au
"Learning, n. The kind of ignorance distinguishing the studious." -- Ambrose Bierce Index: MM-2.6.X/kernel/sched.c =================================================================== --- MM-2.6.X.orig/kernel/sched.c 2006-02-21 16:27:32.000000000 +1100 +++ MM-2.6.X/kernel/sched.c 2006-02-21 17:01:12.000000000 +1100 @@ -169,13 +169,13 @@ #define SCALE_PRIO(x, prio) \ max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO/2), MIN_TIMESLICE) +#define PRIO_TO_TS(sp) \ + ((sp) < NICE_TO_PRIO(0) ? SCALE_PRIO(DEF_TIMESLICE*4, (sp)) : \ + SCALE_PRIO(DEF_TIMESLICE, (sp))) static unsigned int task_timeslice(task_t *p) { - if (p->static_prio < NICE_TO_PRIO(0)) - return SCALE_PRIO(DEF_TIMESLICE*4, p->static_prio); - else - return SCALE_PRIO(DEF_TIMESLICE, p->static_prio); + return PRIO_TO_TS(p->static_prio); } #define task_hot(p, now, sd) ((long long) ((now) - (p)->last_ran) \ < (long long) (sd)->cache_hot_time) @@ -680,11 +680,9 @@ static int effective_prio(task_t *p) */ /* - * Priority weight for load balancing ranges from 1/20 (nice==19) to 459/20 (RT - * priority of 100). + * Priority weight for load balancing ranges (based on time slice allocations). */ -#define NICE_TO_LOAD_PRIO(nice) \ - ((nice >= 0) ? (20 - (nice)) : (20 + (nice) * (nice))) +#define NICE_TO_LOAD_PRIO(nice) PRIO_TO_TS(NICE_TO_PRIO(nice)) #define LOAD_WEIGHT(lp) \ (((lp) * SCHED_LOAD_SCALE) / NICE_TO_LOAD_PRIO(0)) #define NICE_TO_LOAD_WEIGHT(nice) LOAD_WEIGHT(NICE_TO_LOAD_PRIO(nice)) | |