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revert ("sched: fair: weight calculations")

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Yanmin Zhang reported:

Comparing with kernel 2.6.25, sysbench+mysql(oltp, readonly) has many
regressions with 2.6.26-rc1:

 1) 8-core stoakley: 28%;
 2) 16-core tigerton: 20%;
 3) Itanium Montvale: 50%.

Bisect located this patch:

| 8f1bc385cf is first bad commit
| commit 8f1bc385cf
| Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
| Date:   Sat Apr 19 19:45:00 2008 +0200
|
|     sched: fair: weight calculations

Revert it to the 2.6.25 state.

Bisected-by: Yanmin Zhang <yanmin_zhang@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Ingo Molnar 2008-05-29 11:23:17 +02:00
parent f26a398891
commit f9305d4a09
2 changed files with 39 additions and 75 deletions
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9
kernel/sched.c
View file

@ -1368,9 +1368,6 @@ static void __resched_task(struct task_struct *p, int tif_bit)
*/
#define SRR(x, y) (((x) + (1UL << ((y) - 1))) >> (y))
/*
* delta *= weight / lw
*/
static unsigned long
calc_delta_mine(unsigned long delta_exec, unsigned long weight,
struct load_weight *lw)
@ -1393,6 +1390,12 @@ calc_delta_mine(unsigned long delta_exec, unsigned long weight,
return (unsigned long)min(tmp, (u64)(unsigned long)LONG_MAX);
}
static inline unsigned long
calc_delta_fair(unsigned long delta_exec, struct load_weight *lw)
{
return calc_delta_mine(delta_exec, NICE_0_LOAD, lw);
}
static inline void update_load_add(struct load_weight *lw, unsigned long inc)
{
lw->weight += inc;

105
kernel/sched_fair.c
View file

@ -333,34 +333,6 @@ int sched_nr_latency_handler(struct ctl_table *table, int write,
}
#endif
/*
* delta *= w / rw
*/
static inline unsigned long
calc_delta_weight(unsigned long delta, struct sched_entity *se)
{
for_each_sched_entity(se) {
delta = calc_delta_mine(delta,
se->load.weight, &cfs_rq_of(se)->load);
}
return delta;
}
/*
* delta *= rw / w
*/
static inline unsigned long
calc_delta_fair(unsigned long delta, struct sched_entity *se)
{
for_each_sched_entity(se) {
delta = calc_delta_mine(delta,
cfs_rq_of(se)->load.weight, &se->load);
}
return delta;
}
/*
* The idea is to set a period in which each task runs once.
*
@ -390,54 +362,47 @@ static u64 __sched_period(unsigned long nr_running)
*/
static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
return calc_delta_weight(__sched_period(cfs_rq->nr_running), se);
u64 slice = __sched_period(cfs_rq->nr_running);
for_each_sched_entity(se) {
cfs_rq = cfs_rq_of(se);
slice *= se->load.weight;
do_div(slice, cfs_rq->load.weight);
}
return slice;
}
/*
* We calculate the vruntime slice of a to be inserted task
*
* vs = s*rw/w = p
* vs = s/w = p/rw
*/
static u64 sched_vslice_add(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
unsigned long nr_running = cfs_rq->nr_running;
unsigned long weight;
u64 vslice;
if (!se->on_rq)
nr_running++;
return __sched_period(nr_running);
}
/*
* The goal of calc_delta_asym() is to be asymmetrically around NICE_0_LOAD, in
* that it favours >=0 over <0.
*
* -20 |
* |
* 0 --------+-------
* .'
* 19 .'
*
*/
static unsigned long
calc_delta_asym(unsigned long delta, struct sched_entity *se)
{
struct load_weight lw = {
.weight = NICE_0_LOAD,
.inv_weight = 1UL << (WMULT_SHIFT-NICE_0_SHIFT)
};
vslice = __sched_period(nr_running);
for_each_sched_entity(se) {
struct load_weight *se_lw = &se->load;
cfs_rq = cfs_rq_of(se);
if (se->load.weight < NICE_0_LOAD)
se_lw = &lw;
weight = cfs_rq->load.weight;
if (!se->on_rq)
weight += se->load.weight;
delta = calc_delta_mine(delta,
cfs_rq_of(se)->load.weight, se_lw);
vslice *= NICE_0_LOAD;
do_div(vslice, weight);
}
return delta;
return vslice;
}
/*
@ -454,7 +419,11 @@ __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
curr->sum_exec_runtime += delta_exec;
schedstat_add(cfs_rq, exec_clock, delta_exec);
delta_exec_weighted = calc_delta_fair(delta_exec, curr);
delta_exec_weighted = delta_exec;
if (unlikely(curr->load.weight != NICE_0_LOAD)) {
delta_exec_weighted = calc_delta_fair(delta_exec_weighted,
&curr->load);
}
curr->vruntime += delta_exec_weighted;
}
@ -661,17 +630,8 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
if (!initial) {
/* sleeps upto a single latency don't count. */
if (sched_feat(NEW_FAIR_SLEEPERS)) {
unsigned long thresh = sysctl_sched_latency;
/*
* convert the sleeper threshold into virtual time
*/
if (sched_feat(NORMALIZED_SLEEPER))
thresh = calc_delta_fair(thresh, se);
vruntime -= thresh;
}
if (sched_feat(NEW_FAIR_SLEEPERS))
vruntime -= sysctl_sched_latency;
/* ensure we never gain time by being placed backwards. */
vruntime = max_vruntime(se->vruntime, vruntime);
@ -1169,10 +1129,11 @@ static unsigned long wakeup_gran(struct sched_entity *se)
unsigned long gran = sysctl_sched_wakeup_granularity;
/*
* More easily preempt - nice tasks, while not making it harder for
* + nice tasks.
* More easily preempt - nice tasks, while not making
* it harder for + nice tasks.
*/
gran = calc_delta_asym(sysctl_sched_wakeup_granularity, se);
if (unlikely(se->load.weight > NICE_0_LOAD))
gran = calc_delta_fair(gran, &se->load);
return gran;
}