From: Tim Chen <tim.c.chen@linux.intel.com>
To: Shrikanth Hegde <sshegde@linux.vnet.ibm.com>, peterz@infradead.org
Cc: 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: Thu, 27 Jul 2023 06:32:44 -0700 [thread overview]
Message-ID: <6b20e0c0cd82d0d1aafc2a7fb14d9456e19c2c85.camel@linux.intel.com> (raw)
In-Reply-To: <804548a12363479d41dee19bb843002d9e105afd.camel@linux.intel.com>
On Wed, 2023-07-26 at 20:11 -0700, Tim Chen wrote:
> On Mon, 2023-07-17 at 20:28 +0530, Shrikanth Hegde wrote:
> > From: Tim Chen <tim.c.chen@linux.intel.com>
> >
> > 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.
> >
> > Originally-by: Tim Chen <tim.c.chen@linux.intel.com>
> > Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
> > Signed-off-by: Shrikanth Hegde <sshegde@linux.vnet.ibm.com>
> > ---
> > kernel/sched/fair.c | 13 ++++++++++++-
> > 1 file changed, 12 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 932e7b78894a..9502013abe33 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -9532,7 +9532,7 @@ 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;
> >
> > @@ -9720,6 +9720,17 @@ 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;
> > + }
> > + break;
Shrikanth and Peter,
Sorry, I acked Shrikanth's fixup patch too quickly without seeing that Shrikanth added
a "break" in the patch above. My original code did not have that break statement as
I did intend the code to fall through to the "group_fully_busy" code path when
there are no idle cpus in both groups. To make the compiler happy and putting
in the correct logic, I refresh the patch as below.
Thanks.
Tim
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.
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
---
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;
+
case group_fully_busy:
/*
* Select the fully busy group with highest avg_load. In
@@ -9763,7 +9777,7 @@ 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:[~2023-07-27 13:58 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 [this message]
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
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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