From: Tim Chen <tim.c.chen@linux.intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Shrikanth Hegde <sshegde@linux.vnet.ibm.com>,
bristot@redhat.com, bsegall@google.com, dietmar.eggemann@arm.com,
hdanton@sina.com, ionela.voinescu@arm.com, juri.lelli@redhat.com,
len.brown@intel.com, linux-kernel@vger.kernel.org,
mgorman@suse.de, naveen.n.rao@linux.vnet.ibm.com,
rafael.j.wysocki@intel.com, ravi.v.shankar@intel.com,
ricardo.neri@intel.com, rostedt@goodmis.org,
srikar@linux.vnet.ibm.com, srinivas.pandruvada@linux.intel.com,
v-songbaohua@oppo.com, vincent.guittot@linaro.org,
vschneid@redhat.com, x86@kernel.org, yangyicong@hisilicon.com,
yu.c.chen@intel.com
Subject: Re: [PATCH] sched/fair: Add SMT4 group_smt_balance handling
Date: Tue, 05 Sep 2023 10:54:09 -0700 [thread overview]
Message-ID: <0410f8756bbcb2f893622de4e146c13e9565248e.camel@linux.intel.com> (raw)
In-Reply-To: <20230905104136.GC28319@noisy.programming.kicks-ass.net>
On Tue, 2023-09-05 at 12:41 +0200, Peter Zijlstra wrote:
> On Thu, Jul 27, 2023 at 06:32:44AM -0700, Tim Chen wrote:
>
> > kernel/sched/fair.c | 18 ++++++++++++++++--
> > 1 file changed, 16 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index a87988327f88..566686c5f2bd 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -9563,7 +9563,7 @@ static inline long sibling_imbalance(struct lb_env *env,
> > imbalance /= ncores_local + ncores_busiest;
> >
> > /* Take advantage of resource in an empty sched group */
> > - if (imbalance == 0 && local->sum_nr_running == 0 &&
> > + if (imbalance <= 1 && local->sum_nr_running == 0 &&
> > busiest->sum_nr_running > 1)
> > imbalance = 2;
> >
> > @@ -9751,6 +9751,20 @@ static bool update_sd_pick_busiest(struct lb_env *env,
> > break;
> >
> > case group_smt_balance:
> > + /* no idle cpus on both groups handled by group_fully_busy below */
> > + if (sgs->idle_cpus != 0 || busiest->idle_cpus != 0) {
> > + if (sgs->idle_cpus > busiest->idle_cpus)
> > + return false;
> > + if (sgs->idle_cpus < busiest->idle_cpus)
> > + return true;
> > + if (sgs->sum_nr_running <= busiest->sum_nr_running)
> > + return false;
> > + else
> > + return true;
> > + }
> > + goto fully_busy;
> > + break;
>
> This is really daft; why can't this simply be: fallthrough; ? At the
> very least that break must go.
>
>
Yes, the break should go. I was adding the goto to prevent compiler
from complaining about fall through code. The break no longer is needed.
Tim
From 81971a0b1eb64059756f00d8497b1865af2c0792 Mon Sep 17 00:00:00 2001
From: Tim Chen <tim.c.chen@linux.intel.com>
Date: Fri, 14 Jul 2023 16:09:30 -0700
Subject: [PATCH] sched/fair: Add SMT4 group_smt_balance handling
For SMT4, any group with more than 2 tasks will be marked as
group_smt_balance. Retain the behaviour of group_has_spare by marking
the busiest group as the group which has the least number of idle_cpus.
Also, handle rounding effect of adding (ncores_local + ncores_busy)
when the local is fully idle and busy group has more than 2 tasks.
Local group should try to pull at least 1 task in this case.
Fixes: fee1759e4f04 ("sched/fair: Determine active load balance for SMT sched groups")
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
---
kernel/sched/fair.c | 17 +++++++++++++++--
1 file changed, 15 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 0b7445cd5af9..6e7ee2efc1ba 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9575,7 +9575,7 @@ static inline long sibling_imbalance(struct lb_env *env,
imbalance /= ncores_local + ncores_busiest;
/* Take advantage of resource in an empty sched group */
- if (imbalance == 0 && local->sum_nr_running == 0 &&
+ if (imbalance <= 1 && local->sum_nr_running == 0 &&
busiest->sum_nr_running > 1)
imbalance = 2;
@@ -9763,6 +9763,19 @@ static bool update_sd_pick_busiest(struct lb_env *env,
break;
case group_smt_balance:
+ /* no idle cpus on both groups handled by group_fully_busy below */
+ if (sgs->idle_cpus != 0 || busiest->idle_cpus != 0) {
+ if (sgs->idle_cpus > busiest->idle_cpus)
+ return false;
+ if (sgs->idle_cpus < busiest->idle_cpus)
+ return true;
+ if (sgs->sum_nr_running <= busiest->sum_nr_running)
+ return false;
+ else
+ return true;
+ }
+ goto fully_busy;
+
case group_fully_busy:
/*
* Select the fully busy group with highest avg_load. In
@@ -9775,7 +9788,7 @@ static bool update_sd_pick_busiest(struct lb_env *env,
* select the 1st one, except if @sg is composed of SMT
* siblings.
*/
-
+fully_busy:
if (sgs->avg_load < busiest->avg_load)
return false;
--
2.32.0
next prev parent reply other threads:[~2023-09-05 20:05 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-07 22:56 [Patch v3 0/6] Enable Cluster Scheduling for x86 Hybrid CPUs Tim Chen
2023-07-07 22:57 ` [Patch v3 1/6] sched/fair: Determine active load balance for SMT sched groups Tim Chen
2023-07-14 13:06 ` Shrikanth Hegde
2023-07-14 23:05 ` Tim Chen
2023-07-15 18:25 ` Tim Chen
2023-07-16 19:36 ` Shrikanth Hegde
2023-07-17 11:10 ` Peter Zijlstra
2023-07-17 12:18 ` Shrikanth Hegde
2023-07-17 13:37 ` Peter Zijlstra
2023-07-17 14:58 ` [PATCH] sched/fair: Add SMT4 group_smt_balance handling Shrikanth Hegde
2023-07-27 3:11 ` Tim Chen
2023-07-27 13:32 ` Tim Chen
2023-08-07 9:36 ` Shrikanth Hegde
2023-08-21 19:19 ` Tim Chen
2023-09-05 8:03 ` Shrikanth Hegde
2023-09-05 9:49 ` Peter Zijlstra
2023-09-05 18:37 ` Tim Chen
2023-09-06 9:29 ` Shrikanth Hegde
2023-09-06 15:42 ` Tim Chen
2023-09-07 8:58 ` Shrikanth Hegde
2023-09-07 17:42 ` Tim Chen
2023-09-12 10:29 ` [tip: sched/urgent] sched/fair: Fix " tip-bot2 for Tim Chen
2023-09-13 13:11 ` tip-bot2 for Tim Chen
2023-09-05 10:38 ` [PATCH] sched/fair: Add " Peter Zijlstra
2023-09-05 10:41 ` Peter Zijlstra
2023-09-05 17:54 ` Tim Chen [this message]
2023-09-06 8:23 ` Peter Zijlstra
2023-09-06 15:45 ` Tim Chen
2023-07-18 6:07 ` [Patch v3 1/6] sched/fair: Determine active load balance for SMT sched groups Tobias Huschle
2023-07-18 14:52 ` Shrikanth Hegde
2023-07-19 8:14 ` Tobias Huschle
2023-07-14 14:53 ` Tobias Huschle
2023-07-14 23:29 ` Tim Chen
2023-07-07 22:57 ` [Patch v3 2/6] sched/topology: Record number of cores in sched group Tim Chen
2023-07-10 20:33 ` Valentin Schneider
2023-07-10 22:13 ` Tim Chen
2023-07-12 9:27 ` Valentin Schneider
2023-07-10 22:40 ` Tim Chen
2023-07-11 11:31 ` Peter Zijlstra
2023-07-11 16:32 ` Tim Chen
2023-07-07 22:57 ` [Patch v3 3/6] sched/fair: Implement prefer sibling imbalance calculation between asymmetric groups Tim Chen
2023-07-14 13:14 ` Shrikanth Hegde
2023-07-14 14:22 ` Tobias Huschle
2023-07-14 23:35 ` Tim Chen
2023-07-14 20:44 ` Tim Chen
2023-07-14 23:23 ` Tim Chen
2023-07-15 0:11 ` Tim Chen
2023-07-07 22:57 ` [Patch v3 4/6] sched/fair: Consider the idle state of the whole core for load balance Tim Chen
2023-07-14 13:02 ` Shrikanth Hegde
2023-07-14 22:16 ` Tim Chen
2023-07-07 22:57 ` [Patch v3 5/6] sched/x86: Add cluster topology to hybrid CPU Tim Chen
2023-07-08 12:31 ` Peter Zijlstra
2023-07-10 16:13 ` Tim Chen
2023-07-07 22:57 ` [Patch v3 6/6] sched/debug: Dump domains' sched group flags Tim Chen
2023-07-10 20:33 ` Valentin Schneider
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