Messages in this thread Patch in this message | | | Date | Mon, 06 May 2013 12:40:07 +0530 | From | Preeti U Murthy <> | Subject | Re: [PATCH v5 7/7] sched: consider runnable load average in effective_load |
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Hi Alex,Michael,
Can you try out the below patch and check? I have the reason mentioned in the changelog. If this also causes performance regression,you probably need to remove changes made in effective_load() as Michael points out. I believe the below patch should not cause performance regression.
The below patch is a substitute for patch 7.
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sched: Modify effective_load() to use runnable load average
From: Preeti U Murthy <preeti@linux.vnet.ibm.com>
The runqueue weight distribution should update the runnable load average of the cfs_rq on which the task will be woken up.
However since the computation of se->load.weight takes into consideration the runnable load average in update_cfs_shares(),no need to modify this in effective_load(). --- kernel/sched/fair.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 790e23d..5489022 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3045,7 +3045,7 @@ static long effective_load(struct task_group *tg, int cpu, long wl, long wg) /* * w = rw_i + @wl */ - w = se->my_q->load.weight + wl; + w = se->my_q->runnable_load_avg + wl; /* * wl = S * s'_i; see (2) @@ -3066,6 +3066,9 @@ static long effective_load(struct task_group *tg, int cpu, long wl, long wg) /* * wl = dw_i = S * (s'_i - s_i); see (3) */ + /* Do not modify the below as it already contains runnable + * load average in its computation + */ wl -= se->load.weight; /* @@ -3112,14 +3115,14 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) */ if (sync) { tg = task_group(current); - weight = current->se.load.weight; + weight = current->se.avg.load_avg_contrib; this_load += effective_load(tg, this_cpu, -weight, -weight); load += effective_load(tg, prev_cpu, 0, -weight); } tg = task_group(p); - weight = p->se.load.weight; + weight = p->se.avg.load_avg_contrib; /* * In low-load situations, where prev_cpu is idle and this_cpu is idle
Regards Preeti U Murthy
On 05/06/2013 09:04 AM, Michael Wang wrote: > Hi, Alex > > On 05/06/2013 09:45 AM, Alex Shi wrote: >> effective_load calculates the load change as seen from the >> root_task_group. It needs to engage the runnable average >> of changed task. > [snip] >> */ >> @@ -3045,7 +3045,7 @@ static long effective_load(struct task_group *tg, int cpu, long wl, long wg) >> /* >> * w = rw_i + @wl >> */ >> - w = se->my_q->load.weight + wl; >> + w = se->my_q->tg_load_contrib + wl; > > I've tested the patch set, seems like the last patch caused big > regression on pgbench: > > base patch 1~6 patch 1~7 > | db_size | clients | tps | | tps | | tps | > +---------+---------+-------+ +-------+ +-------+ > | 22 MB | 32 | 43420 | | 53387 | | 41625 | > > I guess some magic thing happened in effective_load() while calculating > group decay combined with load decay, what's your opinion? > > Regards, > Michael Wang > >> >> /* >> * wl = S * s'_i; see (2) >> @@ -3066,7 +3066,7 @@ static long effective_load(struct task_group *tg, int cpu, long wl, long wg) >> /* >> * wl = dw_i = S * (s'_i - s_i); see (3) >> */ >> - wl -= se->load.weight; >> + wl -= se->avg.load_avg_contrib; >> >> /* >> * Recursively apply this logic to all parent groups to compute >> @@ -3112,14 +3112,14 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) >> */ >> if (sync) { >> tg = task_group(current); >> - weight = current->se.load.weight; >> + weight = current->se.avg.load_avg_contrib; >> >> this_load += effective_load(tg, this_cpu, -weight, -weight); >> load += effective_load(tg, prev_cpu, 0, -weight); >> } >> >> tg = task_group(p); >> - weight = p->se.load.weight; >> + weight = p->se.avg.load_avg_contrib; >> >> /* >> * In low-load situations, where prev_cpu is idle and this_cpu is idle >> >
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