Peter Zijlstra wrote:
On Thu, 2007-08-30 at 09:50 +0200, Vitaly Mayatskikh wrote:
Short-living process returns its timeslice to the parent, this affects
process that creates a lot of such short-living threads, because its
not a parent for new threads. Patch fixes this issue and doesn't break
kabi as does the patch from reporter: http://lkml.org/lkml/2007/4/7/21
plain text document attachment (2.6.21-timeslice.patch), "proposed
patch"
diff -up -bB ./include/linux/sched.h.orig ./include/linux/sched.h
--- ./include/linux/sched.h.orig 2007-08-21 09:20:22.000000000 +0200
+++ ./include/linux/sched.h 2007-08-27 10:14:06.000000000 +0200
@@ -827,7 +827,9 @@ struct task_struct {
unsigned long policy;
cpumask_t cpus_allowed;
- unsigned int time_slice, first_time_slice;
+ unsigned int time_slice;
+ /* Pid of creator */
+ unsigned int cpid;
might as well make that pid_t, or maybe even a struct pid* and keep a
reference on it - the struct pid police might have an opinion.
Store the struct pid reference itself. In any case you make
the find_get_pid() later to obtain the struct pid itself. This
will even make the sched_exit() work faster.
#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
struct sched_info sched_info;
diff -up -bB ./kernel/sched.c.orig ./kernel/sched.c
--- ./kernel/sched.c.orig 2007-08-21 09:20:22.000000000 +0200
+++ ./kernel/sched.c 2007-08-27 10:18:44.000000000 +0200
@@ -1626,9 +1626,9 @@ void fastcall sched_fork(struct task_str
p->time_slice = (current->time_slice + 1) >> 1;
/*
* The remainder of the first timeslice might be recovered by
- * the parent if the child exits early enough.
+ * the creator (not parent!) if the child exits early enough.
*/
- p->first_time_slice = 1;
+ p->cpid = current->pid;
current->time_slice >>= 1;
p->timestamp = sched_clock();
if (unlikely(!current->time_slice)) {
@@ -1728,33 +1728,46 @@ void fastcall wake_up_new_task(struct ta
/*
* Potentially available exiting-child timeslices are
- * retrieved here - this way the parent does not get
+ * retrieved here - this way the creator does not get
* penalized for creating too many threads.
*
* (this cannot be used to 'generate' timeslices
* artificially, because any timeslice recovered here
- * was given away by the parent in the first place.)
+ * was given away by the creator in the first place.)
*/
void fastcall sched_exit(struct task_struct *p)
{
unsigned long flags;
struct rq *rq;
-
+ struct task_struct* creator = NULL;
/*
* If the child was a (relative-) CPU hog then decrease
- * the sleep_avg of the parent as well.
+ * the sleep_avg of the creator as well.
*/
- rq = task_rq_lock(p->parent, &flags);
- if (p->first_time_slice && task_cpu(p) == task_cpu(p->parent)) {
- p->parent->time_slice += p->time_slice;
- if (unlikely(p->parent->time_slice > task_timeslice(p)))
- p->parent->time_slice = task_timeslice(p);
+ if (p->cpid) {
+ struct pid *pid = find_get_pid((pid_t)p->cpid);
+ if (pid) {
+ creator = get_pid_task(pid, PIDTYPE_PID);
+ put_pid(pid);
}
- if (p->sleep_avg < p->parent->sleep_avg)
- p->parent->sleep_avg = p->parent->sleep_avg /
+
+ if (creator) {
+ if (task_cpu(p) == task_cpu(creator)) {
+ rq = task_rq_lock(creator, &flags);
+
+ creator->time_slice += p->time_slice;
+ if (unlikely(creator->time_slice > task_timeslice(p)))
+ creator->time_slice = task_timeslice(p);
+
+ if (p->sleep_avg < creator->sleep_avg)
+ creator->sleep_avg = creator->sleep_avg /
(EXIT_WEIGHT + 1) * EXIT_WEIGHT + p->sleep_avg /
(EXIT_WEIGHT + 1);
task_rq_unlock(rq, &flags);
+ }
+ put_task_struct(creator);
+ }
+ }
}
/**
@@ -3153,7 +3166,7 @@ static void task_running_tick(struct rq
*/
if ((p->policy == SCHED_RR) && !--p->time_slice) {
p->time_slice = task_timeslice(p);
- p->first_time_slice = 0;
+ p->cpid = 0;
set_tsk_need_resched(p);
/* put it at the end of the queue: */
@@ -3166,7 +3179,7 @@ static void task_running_tick(struct rq
set_tsk_need_resched(p);
p->prio = effective_prio(p);
p->time_slice = task_timeslice(p);
- p->first_time_slice = 0;
+ p->cpid = 0;
if (!rq->expired_timestamp)
rq->expired_timestamp = jiffies;
Other than that it looks good, pretty much what I suggested :-)
-
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