Messages in this thread Patch in this message | | | Date | Sun, 29 Jan 2006 10:44:17 +1100 | From | Peter Williams <> | Subject | Re: [ANNOUNCE][RFC] PlugSched-6.2 for 2.6.16-rc1 and 2.6.16-rc1-mm1 |
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Peter Williams wrote: > Paolo Ornati wrote: > >> On Thu, 26 Jan 2006 12:09:53 +1100 >> Peter Williams <pwil3058@bigpond.net.au> wrote: >> >> >>> I know that I've said this before but I've found the problem. >>> Embarrassingly, it was a basic book keeping error (recently >>> introduced and equivalent to getting nr_running wrong for each CPU) >>> in the gathering of the statistics that I use. :-( >>> >>> The attached patch (applied on top of the PlugSched patch) should fix >>> things. Could you test it please? >> >> >> >> Ok, this one make a difference: >> >> (transcode) >> >> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND >> 5774 paolo 34 0 116m 18m 2432 R 86.2 3.7 0:11.65 transcode >> 5788 paolo 32 0 51000 4472 1872 S 7.5 0.9 0:01.13 tcdecode >> 5797 paolo 29 0 4948 1468 372 D 3.2 0.3 0:00.30 dd >> 5781 paolo 33 0 19844 1092 880 S 1.0 0.2 0:00.10 tcdemux >> 5783 paolo 31 0 47964 2496 1956 S 0.7 0.5 0:00.08 tcdecode >> 5786 paolo 34 0 19840 1088 880 R 0.5 0.2 0:00.06 tcdemux >> >> (sched_fooler) >> >> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND >> 5804 paolo 34 0 2396 292 228 R 35.7 0.1 0:12.84 a.out >> 5803 paolo 34 0 2392 288 228 R 30.5 0.1 0:11.49 a.out >> 5805 paolo 34 0 2392 288 228 R 30.2 0.1 0:10.70 a.out >> 5815 paolo 29 0 4948 1468 372 D 3.7 0.3 0:00.29 dd >> 5458 paolo 28 0 86656 21m 15m S 0.2 4.4 0:02.18 konsole >> >> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND >> 5804 paolo 34 0 2396 292 228 R 36.5 0.1 0:38.19 a.out >> 5803 paolo 34 0 2392 288 228 R 30.5 0.1 0:34.27 a.out >> 5805 paolo 34 0 2392 288 228 R 29.2 0.1 0:32.39 a.out >> 5829 paolo 34 0 4952 1472 372 R 3.2 0.3 0:00.35 dd >> >> DD_TEST + sched_fooler: 512 MB --- ~20s instead of 16.6s >> >> This is a clear improvement... however I wonder why DD priority >> fluctuate going up even to 34 (the range is something like 29 <---> >> 34). >> > > It's because the "fairness" bonus is still being done as a one shot > bonus when a task's delay time become unfairly large. I mentioned this > before as possibly needing to be changed to a more persistent model but > after I discovered the accounting bug I deferred doing anything about it > in the hope that fixing the bug would have been sufficient. > > I'll now try a model whereby a task's fairness bonus is increased > whenever it has unfair delays and decreased when it doesn't. Hopefully, > with the right rates of increase/decrease, this can result in a system > where a task has a fairly persistent bonus which is sufficient to give > it its fair share. One reason that I've been avoiding this method is > that it introduces double smoothing: once in the calculation of the > average delay time and then again in the determination of the bonus; and > I'm concerned this may make it slow to react to change. Any way I'll > give it a try and see what happens.
Attached is a patch which makes the fairness bonuses more persistent. I should be applied on top of the last patch that I sent. Could you test it please?
Thanks Peter -- Peter Williams pwil3058@bigpond.net.au
"Learning, n. The kind of ignorance distinguishing the studious." -- Ambrose Bierce Index: MM-2.6.16/kernel/sched_spa_ws.c =================================================================== --- MM-2.6.16.orig/kernel/sched_spa_ws.c 2006-01-26 12:21:50.000000000 +1100 +++ MM-2.6.16/kernel/sched_spa_ws.c 2006-01-29 10:00:21.000000000 +1100 @@ -45,12 +45,20 @@ static unsigned int initial_ia_bonus = D #define LSHARES_AVG_ALPHA ((1 << LSHARES_AVG_OFFSET) - 2) #define LSHARES_AVG_INCR(a) ((a) << 1) #define LSHARES_AVG_REAL(s) ((s) << LSHARES_AVG_OFFSET) -#define LSHARES_AVG_ONE LSAHRES_AVG_REAL(1UL) +#define LSHARES_AVG_ONE LSHARES_AVG_REAL(1UL) #define LSHARES_AVG_MUL(a, b) (((a) * (b)) >> LSHARES_AVG_OFFSET) static unsigned int max_fairness_bonus = DEF_MAX_FAIRNESS_BONUS; -#define FAIRNESS_BONUS_OFFSET 8 +#define FAIRNESS_BONUS_OFFSET 5 +#define FAIRNESS_ALPHA ((1UL << FAIRNESS_BONUS_OFFSET) - 2) +#define FAIRNESS_ALPHA_COMPL 2 + +static inline int fairness_bonus(const struct task_struct *p) +{ + return (p->sdu.spa.auxilary_bonus * max_fairness_bonus) >> + FAIRNESS_BONUS_OFFSET; +} static DEFINE_PER_CPU(unsigned long, rq_avg_lshares); @@ -124,7 +132,7 @@ static inline void zero_interactive_bonu static inline int bonuses(const struct task_struct *p) { - return current_ia_bonus_rnd(p) + p->sdu.spa.auxilary_bonus; + return current_ia_bonus_rnd(p) + fairness_bonus(p); } static int spa_ws_effective_prio(const struct task_struct *p) @@ -161,65 +169,22 @@ static void spa_ws_fork(struct task_stru p->sdu.spa.interactive_bonus <<= IA_BONUS_OFFSET; } -static inline unsigned int map_ratio(unsigned long long a, - unsigned long long b, - unsigned int range) -{ - a *= range; - -#if BITS_PER_LONG < 64 - /* - * Assume that there's no 64 bit divide available - */ - if (a < b) - return 0; - /* - * Scale down until b less than 32 bits so that we can do - * a divide using do_div() - */ - while (b > ULONG_MAX) { a >>= 1; b >>= 1; } - - (void)do_div(a, (unsigned long)b); - - return a; -#else - return a / b; -#endif -} - static void spa_ws_reassess_fairness_bonus(struct task_struct *p) { - unsigned long long expected_delay, adjusted_delay; - unsigned long long avg_lshares; - unsigned long pshares; - - p->sdu.spa.auxilary_bonus = 0; - if (max_fairness_bonus == 0) - return; + unsigned long long expected_delay; + unsigned long long wanr; /* weighted average number running */ - pshares = LSHARES_AVG_REAL(p->sdu.spa.eb_shares); - avg_lshares = per_cpu(rq_avg_lshares, task_cpu(p)); - if (avg_lshares <= pshares) + wanr = per_cpu(rq_avg_lshares, task_cpu(p)) / p->sdu.spa.eb_shares; + if (wanr <= LSHARES_AVG_ONE) expected_delay = 0; - else { - expected_delay = p->sdu.spa.avg_cpu_per_cycle * - (avg_lshares - pshares); - (void)do_div(expected_delay, pshares); - } - - /* - * No delay means no bonus, but - * NB this test also avoids a possible divide by zero error if - * cpu is also zero and negative bonuses - */ - if (p->sdu.spa.avg_delay_per_cycle <= expected_delay) - return; - - adjusted_delay = p->sdu.spa.avg_delay_per_cycle - expected_delay; - p->sdu.spa.auxilary_bonus = - map_ratio(adjusted_delay, - adjusted_delay + p->sdu.spa.avg_cpu_per_cycle, - max_fairness_bonus); + else + expected_delay = LSHARES_AVG_MUL(p->sdu.spa.avg_cpu_per_cycle, + (wanr - LSHARES_AVG_ONE)); + + p->sdu.spa.auxilary_bonus *= FAIRNESS_ALPHA; + p->sdu.spa.auxilary_bonus >>= FAIRNESS_BONUS_OFFSET; + if (p->sdu.spa.avg_delay_per_cycle > expected_delay) + p->sdu.spa.auxilary_bonus += FAIRNESS_ALPHA_COMPL; } static inline int spa_ws_eligible(struct task_struct *p) | |