Commit a4ec24b48ddef1e93f7578be53270f0b95ad666c
Committed by
Ingo Molnar
Ingo Molnar
1 parent
a9957449b0
Exists in
master
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39 other branches
sched: tidy up SCHED_RR
- make timeslices of SCHED_RR tasks constant and not dependent on task's static_prio [1] ; - remove obsolete code (timeslice related bits); - make sched_rr_get_interval() return something more meaningful [2] for SCHED_OTHER tasks. [1] according to the following link, it's not compliant with SUSv3 (not sure though, what is the reference for us :-) http://lkml.org/lkml/2007/3/7/656 [2] the interval is dynamic and can be depicted as follows "should a task be one of the runnable tasks at this particular moment, it would expect to run for this interval of time before being re-scheduled by the scheduler tick". (i.e. it's more precise if a task is runnable at the moment) yeah, this seems to require task_rq_lock/unlock() but this is not a hot path. results: (SCHED_FIFO) dimm@earth:~/storage/prog$ sudo chrt -f 10 ./rr_interval time_slice: 0 : 0 (SCHED_RR) dimm@earth:~/storage/prog$ sudo chrt 10 ./rr_interval time_slice: 0 : 99984800 (SCHED_NORMAL) dimm@earth:~/storage/prog$ ./rr_interval time_slice: 0 : 19996960 (SCHED_NORMAL + a cpu_hog of similar 'weight' on the same CPU --- so should be a half of the previous result) dimm@earth:~/storage/prog$ taskset 1 ./rr_interval time_slice: 0 : 9998480 Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Showing 2 changed files with 18 additions and 25 deletions Side-by-side Diff
kernel/sched.c
| ... | ... | @@ -96,7 +96,7 @@ |
| 96 | 96 | /* |
| 97 | 97 | * Some helpers for converting nanosecond timing to jiffy resolution |
| 98 | 98 | */ |
| 99 | -#define NS_TO_JIFFIES(TIME) ((TIME) / (1000000000 / HZ)) | |
| 99 | +#define NS_TO_JIFFIES(TIME) ((unsigned long)(TIME) / (1000000000 / HZ)) | |
| 100 | 100 | #define JIFFIES_TO_NS(TIME) ((TIME) * (1000000000 / HZ)) |
| 101 | 101 | |
| 102 | 102 | #define NICE_0_LOAD SCHED_LOAD_SCALE |
| 103 | 103 | |
| ... | ... | @@ -105,11 +105,9 @@ |
| 105 | 105 | /* |
| 106 | 106 | * These are the 'tuning knobs' of the scheduler: |
| 107 | 107 | * |
| 108 | - * Minimum timeslice is 5 msecs (or 1 jiffy, whichever is larger), | |
| 109 | - * default timeslice is 100 msecs, maximum timeslice is 800 msecs. | |
| 108 | + * default timeslice is 100 msecs (used only for SCHED_RR tasks). | |
| 110 | 109 | * Timeslices get refilled after they expire. |
| 111 | 110 | */ |
| 112 | -#define MIN_TIMESLICE max(5 * HZ / 1000, 1) | |
| 113 | 111 | #define DEF_TIMESLICE (100 * HZ / 1000) |
| 114 | 112 | |
| 115 | 113 | #ifdef CONFIG_SMP |
| ... | ... | @@ -133,24 +131,6 @@ |
| 133 | 131 | } |
| 134 | 132 | #endif |
| 135 | 133 | |
| 136 | -#define SCALE_PRIO(x, prio) \ | |
| 137 | - max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO / 2), MIN_TIMESLICE) | |
| 138 | - | |
| 139 | -/* | |
| 140 | - * static_prio_timeslice() scales user-nice values [ -20 ... 0 ... 19 ] | |
| 141 | - * to time slice values: [800ms ... 100ms ... 5ms] | |
| 142 | - */ | |
| 143 | -static unsigned int static_prio_timeslice(int static_prio) | |
| 144 | -{ | |
| 145 | - if (static_prio == NICE_TO_PRIO(19)) | |
| 146 | - return 1; | |
| 147 | - | |
| 148 | - if (static_prio < NICE_TO_PRIO(0)) | |
| 149 | - return SCALE_PRIO(DEF_TIMESLICE * 4, static_prio); | |
| 150 | - else | |
| 151 | - return SCALE_PRIO(DEF_TIMESLICE, static_prio); | |
| 152 | -} | |
| 153 | - | |
| 154 | 134 | static inline int rt_policy(int policy) |
| 155 | 135 | { |
| 156 | 136 | if (unlikely(policy == SCHED_FIFO) || unlikely(policy == SCHED_RR)) |
| ... | ... | @@ -4746,6 +4726,7 @@ |
| 4746 | 4726 | long sys_sched_rr_get_interval(pid_t pid, struct timespec __user *interval) |
| 4747 | 4727 | { |
| 4748 | 4728 | struct task_struct *p; |
| 4729 | + unsigned int time_slice; | |
| 4749 | 4730 | int retval = -EINVAL; |
| 4750 | 4731 | struct timespec t; |
| 4751 | 4732 | |
| 4752 | 4733 | |
| ... | ... | @@ -4762,9 +4743,21 @@ |
| 4762 | 4743 | if (retval) |
| 4763 | 4744 | goto out_unlock; |
| 4764 | 4745 | |
| 4765 | - jiffies_to_timespec(p->policy == SCHED_FIFO ? | |
| 4766 | - 0 : static_prio_timeslice(p->static_prio), &t); | |
| 4746 | + if (p->policy == SCHED_FIFO) | |
| 4747 | + time_slice = 0; | |
| 4748 | + else if (p->policy == SCHED_RR) | |
| 4749 | + time_slice = DEF_TIMESLICE; | |
| 4750 | + else { | |
| 4751 | + struct sched_entity *se = &p->se; | |
| 4752 | + unsigned long flags; | |
| 4753 | + struct rq *rq; | |
| 4754 | + | |
| 4755 | + rq = task_rq_lock(p, &flags); | |
| 4756 | + time_slice = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se)); | |
| 4757 | + task_rq_unlock(rq, &flags); | |
| 4758 | + } | |
| 4767 | 4759 | read_unlock(&tasklist_lock); |
| 4760 | + jiffies_to_timespec(time_slice, &t); | |
| 4768 | 4761 | retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0; |
| 4769 | 4762 | out_nounlock: |
| 4770 | 4763 | return retval; |
kernel/sched_rt.c