From: Vincent Guittot <vincent.guittot@linaro.org>
To: linux-kernel@vger.kernel.org, mingo@redhat.com, peterz@infradead.org
Cc: pauld@redhat.com, valentin.schneider@arm.com,
srikar@linux.vnet.ibm.com, quentin.perret@arm.com,
dietmar.eggemann@arm.com, Morten.Rasmussen@arm.com,
hdanton@sina.com, Vincent Guittot <vincent.guittot@linaro.org>
Subject: [PATCH v3 10/10] sched/fair: optimize find_idlest_group
Date: Thu, 19 Sep 2019 09:33:41 +0200 [thread overview]
Message-ID: <1568878421-12301-11-git-send-email-vincent.guittot@linaro.org> (raw)
In-Reply-To: <1568878421-12301-1-git-send-email-vincent.guittot@linaro.org>
find_idlest_group() now loads CPU's load_avg in 2 different ways.
Consolidate the function to read and use load_avg only once and simplify
the algorithm to only look for the group with lowest load_avg.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
---
kernel/sched/fair.c | 52 +++++++++++-----------------------------------------
1 file changed, 11 insertions(+), 41 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 39a37ae..1fac444 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5560,16 +5560,14 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p,
{
struct sched_group *idlest = NULL, *group = sd->groups;
struct sched_group *most_spare_sg = NULL;
- unsigned long min_runnable_load = ULONG_MAX;
- unsigned long this_runnable_load = ULONG_MAX;
- unsigned long min_avg_load = ULONG_MAX, this_avg_load = ULONG_MAX;
+ unsigned long min_load = ULONG_MAX, this_load = ULONG_MAX;
unsigned long most_spare = 0, this_spare = 0;
int imbalance_scale = 100 + (sd->imbalance_pct-100)/2;
unsigned long imbalance = scale_load_down(NICE_0_LOAD) *
(sd->imbalance_pct-100) / 100;
do {
- unsigned long load, avg_load, runnable_load;
+ unsigned long load;
unsigned long spare_cap, max_spare_cap;
int local_group;
int i;
@@ -5586,15 +5584,11 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p,
* Tally up the load of all CPUs in the group and find
* the group containing the CPU with most spare capacity.
*/
- avg_load = 0;
- runnable_load = 0;
+ load = 0;
max_spare_cap = 0;
for_each_cpu(i, sched_group_span(group)) {
- load = cpu_load(cpu_rq(i));
- runnable_load += load;
-
- avg_load += cfs_rq_load_avg(&cpu_rq(i)->cfs);
+ load += cpu_load(cpu_rq(i));
spare_cap = capacity_spare_without(i, p);
@@ -5603,31 +5597,15 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p,
}
/* Adjust by relative CPU capacity of the group */
- avg_load = (avg_load * SCHED_CAPACITY_SCALE) /
- group->sgc->capacity;
- runnable_load = (runnable_load * SCHED_CAPACITY_SCALE) /
+ load = (load * SCHED_CAPACITY_SCALE) /
group->sgc->capacity;
if (local_group) {
- this_runnable_load = runnable_load;
- this_avg_load = avg_load;
+ this_load = load;
this_spare = max_spare_cap;
} else {
- if (min_runnable_load > (runnable_load + imbalance)) {
- /*
- * The runnable load is significantly smaller
- * so we can pick this new CPU:
- */
- min_runnable_load = runnable_load;
- min_avg_load = avg_load;
- idlest = group;
- } else if ((runnable_load < (min_runnable_load + imbalance)) &&
- (100*min_avg_load > imbalance_scale*avg_load)) {
- /*
- * The runnable loads are close so take the
- * blocked load into account through avg_load:
- */
- min_avg_load = avg_load;
+ if (load < min_load) {
+ min_load = load;
idlest = group;
}
@@ -5668,18 +5646,10 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p,
* local domain to be very lightly loaded relative to the remote
* domains but "imbalance" skews the comparison making remote CPUs
* look much more favourable. When considering cross-domain, add
- * imbalance to the runnable load on the remote node and consider
- * staying local.
+ * imbalance to the load on the remote node and consider staying
+ * local.
*/
- if ((sd->flags & SD_NUMA) &&
- min_runnable_load + imbalance >= this_runnable_load)
- return NULL;
-
- if (min_runnable_load > (this_runnable_load + imbalance))
- return NULL;
-
- if ((this_runnable_load < (min_runnable_load + imbalance)) &&
- (100*this_avg_load < imbalance_scale*min_avg_load))
+ if (min_load + imbalance >= this_load)
return NULL;
return idlest;
--
2.7.4
next prev parent reply other threads:[~2019-09-19 7:34 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-19 7:33 [PATCH v3 0/8] sched/fair: rework the CFS load balance Vincent Guittot
2019-09-19 7:33 ` [PATCH v3 01/10] sched/fair: clean up asym packing Vincent Guittot
2019-09-27 23:57 ` Rik van Riel
2019-09-19 7:33 ` [PATCH v3 02/10] sched/fair: rename sum_nr_running to sum_h_nr_running Vincent Guittot
2019-09-27 23:59 ` Rik van Riel
2019-10-01 17:11 ` Valentin Schneider
2019-09-19 7:33 ` [PATCH v3 03/10] sched/fair: remove meaningless imbalance calculation Vincent Guittot
2019-09-28 0:05 ` Rik van Riel
2019-10-01 17:12 ` Valentin Schneider
2019-10-02 6:28 ` Vincent Guittot
2019-09-19 7:33 ` [PATCH v3 04/10] sched/fair: rework load_balance Vincent Guittot
2019-09-30 1:12 ` Rik van Riel
2019-09-30 7:44 ` Vincent Guittot
2019-09-30 16:24 ` Dietmar Eggemann
2019-10-01 8:14 ` Vincent Guittot
2019-10-01 16:52 ` Dietmar Eggemann
2019-10-02 6:44 ` Vincent Guittot
2019-10-02 9:21 ` Dietmar Eggemann
2019-10-08 13:02 ` Peter Zijlstra
2019-10-02 8:23 ` Vincent Guittot
2019-10-02 9:24 ` Dietmar Eggemann
2019-10-01 8:15 ` Dietmar Eggemann
2019-10-01 9:14 ` Vincent Guittot
2019-10-01 16:57 ` Dietmar Eggemann
2019-10-01 17:47 ` Valentin Schneider
2019-10-02 8:30 ` Vincent Guittot
2019-10-02 10:47 ` Valentin Schneider
2019-10-08 14:16 ` Peter Zijlstra
2019-10-08 14:34 ` Valentin Schneider
2019-10-08 15:30 ` Vincent Guittot
2019-10-08 15:48 ` Valentin Schneider
2019-10-08 17:39 ` Peter Zijlstra
2019-10-08 18:45 ` Vincent Guittot
2019-10-08 16:33 ` Peter Zijlstra
2019-10-08 16:39 ` Valentin Schneider
2019-10-08 17:36 ` Valentin Schneider
2019-10-08 17:55 ` Peter Zijlstra
2019-10-08 18:47 ` Vincent Guittot
2019-10-16 7:21 ` Parth Shah
2019-10-16 11:56 ` Vincent Guittot
2019-10-18 5:34 ` Parth Shah
2019-09-19 7:33 ` [PATCH v3 05/10] sched/fair: use rq->nr_running when balancing load Vincent Guittot
2019-09-19 7:33 ` [PATCH v3 06/10] sched/fair: use load instead of runnable load in load_balance Vincent Guittot
2019-09-19 7:33 ` [PATCH v3 07/10] sched/fair: evenly spread tasks when not overloaded Vincent Guittot
2019-09-19 7:33 ` [PATCH v3 08/10] sched/fair: use utilization to select misfit task Vincent Guittot
2019-10-01 17:12 ` Valentin Schneider
2019-09-19 7:33 ` [PATCH v3 09/10] sched/fair: use load instead of runnable load in wakeup path Vincent Guittot
2019-10-07 15:14 ` Rik van Riel
2019-10-07 15:27 ` Vincent Guittot
2019-10-07 18:06 ` Rik van Riel
2019-09-19 7:33 ` Vincent Guittot [this message]
2019-10-08 14:32 ` [PATCH v3 0/8] sched/fair: rework the CFS load balance Phil Auld
2019-10-08 15:53 ` Vincent Guittot
2019-10-09 19:33 ` Phil Auld
2019-10-10 8:20 ` Vincent Guittot
2019-10-16 7:21 ` Parth Shah
2019-10-16 11:51 ` Vincent Guittot
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1568878421-12301-11-git-send-email-vincent.guittot@linaro.org \
--to=vincent.guittot@linaro.org \
--cc=Morten.Rasmussen@arm.com \
--cc=dietmar.eggemann@arm.com \
--cc=hdanton@sina.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=pauld@redhat.com \
--cc=peterz@infradead.org \
--cc=quentin.perret@arm.com \
--cc=srikar@linux.vnet.ibm.com \
--cc=valentin.schneider@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).