From: Valentin Schneider <vschneid@redhat.com>
To: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Cc: Ionela Voinescu <ionela.voinescu@arm.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Ricardo Neri <ricardo.neri@intel.com>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
Ben Segall <bsegall@google.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Len Brown <len.brown@intel.com>, Mel Gorman <mgorman@suse.de>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
Steven Rostedt <rostedt@goodmis.org>,
Tim Chen <tim.c.chen@linux.intel.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
"Tim C . Chen" <tim.c.chen@intel.com>
Subject: Re: [PATCH v2 5/7] x86/sched: Remove SD_ASYM_PACKING from the "SMT" domain
Date: Thu, 22 Dec 2022 16:56:51 +0000 [thread overview]
Message-ID: <xhsmhr0wre5rg.mognet@vschneid.remote.csb> (raw)
In-Reply-To: <20221220004238.GB23844@ranerica-svr.sc.intel.com>
On 19/12/22 16:42, Ricardo Neri wrote:
> On Thu, Dec 15, 2022 at 04:48:14PM +0000, Valentin Schneider wrote:
>> With that said, so far all but one flag (SD_PREFER_SIBLING, and that's
>> because of big.LITTLE woes) follow the SDF_SHARED_{CHILD, PARENT} pattern,
>> if SD_ASYM_PACKING no longer does then we need to think whether we're
>> trying to make it do funky things.
>
> My thesis is that x86 does not need the SD_ASYM_PACKING flag at the SMT
> level because all SMT siblings are identical. There are cores of higher
> priority at the "MC" level (maybe in the future at the "CLS" level).
>
> Power7 is fine because it only uses SD_ASYM_PACKING at the SMT level.
>
So with what I groked from your series, I agree with you, x86 shouldn't
need it at SMT level.
What about the below?
---
diff --git a/include/linux/sched/sd_flags.h b/include/linux/sched/sd_flags.h
index 57bde66d95f7a..8dc16942135b4 100644
--- a/include/linux/sched/sd_flags.h
+++ b/include/linux/sched/sd_flags.h
@@ -132,12 +132,12 @@ SD_FLAG(SD_SERIALIZE, SDF_SHARED_PARENT | SDF_NEEDS_GROUPS)
/*
* Place busy tasks earlier in the domain
*
- * SHARED_CHILD: Usually set on the SMT level. Technically could be set further
- * up, but currently assumed to be set from the base domain
- * upwards (see update_top_cache_domain()).
+ * SHARED_PARENT: Usually set on the SMT level. Can be set further up if all
+ * siblings of an SMT core are identical, but SMT cores themselves
+ * have different priorites.
* NEEDS_GROUPS: Load balancing flag.
*/
-SD_FLAG(SD_ASYM_PACKING, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS)
+SD_FLAG(SD_ASYM_PACKING, SDF_SHARED_PARENT | SDF_NEEDS_GROUPS)
/*
* Prefer to place tasks in a sibling domain
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index b1d338a740e56..2d532e29373b1 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1772,6 +1772,19 @@ queue_balance_callback(struct rq *rq,
for (__sd = rcu_dereference_check_sched_domain(cpu_rq(cpu)->sd); \
__sd; __sd = __sd->parent)
+static inline struct sched_domain *__highest_flag_domain(struct sched_domain *sd, int flag)
+{
+ struct sched_domain *hsd = NULL;
+
+ for (; sd; sd = sd->parent) {
+ if (!(sd->flags & flag))
+ break;
+ hsd = sd;
+ }
+
+ return hsd;
+}
+
/**
* highest_flag_domain - Return highest sched_domain containing flag.
* @cpu: The CPU whose highest level of sched domain is to
@@ -1783,15 +1796,7 @@ queue_balance_callback(struct rq *rq,
*/
static inline struct sched_domain *highest_flag_domain(int cpu, int flag)
{
- struct sched_domain *sd, *hsd = NULL;
-
- for_each_domain(cpu, sd) {
- if (!(sd->flags & flag))
- break;
- hsd = sd;
- }
-
- return hsd;
+ return __highest_flag_domain(rcu_dereference_check_sched_domain(cpu_rq(cpu)->sd), flag);
}
static inline struct sched_domain *lowest_flag_domain(int cpu, int flag)
@@ -1806,6 +1811,16 @@ static inline struct sched_domain *lowest_flag_domain(int cpu, int flag)
return sd;
}
+static inline struct sched_domain *highest_parent_flag_domain(int cpu, int flag)
+{
+ struct sched_domain *sd;
+
+ SCHED_WARN_ON(!(sd_flag_debug[ilog2(flag)].meta_flags & SDF_SHARED_PARENT));
+
+ sd = lowest_flag_domain(cpu, flag);
+ return __highest_flag_domain(sd, flag);
+}
+
DECLARE_PER_CPU(struct sched_domain __rcu *, sd_llc);
DECLARE_PER_CPU(int, sd_llc_size);
DECLARE_PER_CPU(int, sd_llc_id);
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 8154ef590b9f8..4e0e5b27c331b 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -692,7 +692,7 @@ static void update_top_cache_domain(int cpu)
sd = lowest_flag_domain(cpu, SD_NUMA);
rcu_assign_pointer(per_cpu(sd_numa, cpu), sd);
- sd = highest_flag_domain(cpu, SD_ASYM_PACKING);
+ sd = highest_parent_flag_domain(cpu, SD_ASYM_PACKING);
rcu_assign_pointer(per_cpu(sd_asym_packing, cpu), sd);
sd = lowest_flag_domain(cpu, SD_ASYM_CPUCAPACITY_FULL);
next prev parent reply other threads:[~2022-12-22 16:57 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-22 20:35 [PATCH v2 0/7] x86/sched: Avoid unnecessary migrations within SMT domains Ricardo Neri
2022-11-22 20:35 ` [PATCH v2 1/7] sched/fair: Generalize asym_packing logic for SMT local sched group Ricardo Neri
2022-12-06 17:22 ` Dietmar Eggemann
2022-12-12 17:53 ` Ricardo Neri
2022-12-21 13:03 ` Dietmar Eggemann
2022-12-22 4:32 ` Ricardo Neri
2022-12-22 11:12 ` Dietmar Eggemann
2022-12-23 13:11 ` Ricardo Neri
2022-12-22 16:55 ` Valentin Schneider
2022-12-29 4:00 ` Ricardo Neri
2023-01-11 16:04 ` Valentin Schneider
2023-01-13 19:02 ` Ricardo Neri
2023-01-16 4:05 ` Ricardo Neri
2023-01-16 19:07 ` Valentin Schneider
2023-01-17 12:49 ` Ricardo Neri
2022-11-22 20:35 ` [PATCH v2 2/7] sched: Prepare sched_asym_prefer() to handle idle state of SMT siblings Ricardo Neri
2022-11-22 20:35 ` [PATCH v2 3/7] sched: Teach arch_asym_cpu_priority() the " Ricardo Neri
2022-12-06 17:54 ` Dietmar Eggemann
2022-12-12 17:54 ` Ricardo Neri
2022-12-21 17:12 ` Dietmar Eggemann
2022-12-22 4:55 ` Ricardo Neri
2022-12-22 16:56 ` Valentin Schneider
2022-11-22 20:35 ` [PATCH v2 4/7] sched/fair: Introduce sched_smt_siblings_idle() Ricardo Neri
2022-12-06 18:03 ` Dietmar Eggemann
2022-12-12 17:54 ` Ricardo Neri
2022-12-22 11:12 ` Dietmar Eggemann
2022-12-22 16:56 ` Valentin Schneider
2022-12-24 5:28 ` Ricardo Neri
2022-12-28 15:29 ` Chen Yu
2022-12-30 0:17 ` Ricardo Neri
2023-01-10 19:21 ` Valentin Schneider
2022-11-22 20:35 ` [PATCH v2 5/7] x86/sched: Remove SD_ASYM_PACKING from the "SMT" domain Ricardo Neri
2022-12-08 16:03 ` Ionela Voinescu
2022-12-14 16:59 ` Ricardo Neri
2022-12-15 16:48 ` Valentin Schneider
2022-12-20 0:42 ` Ricardo Neri
2022-12-22 16:56 ` Valentin Schneider [this message]
2022-12-29 19:02 ` Ricardo Neri
2023-01-10 19:17 ` Valentin Schneider
2023-01-13 1:31 ` Ricardo Neri
2022-11-22 20:35 ` [PATCH v2 6/7] x86/sched/itmt: Give all SMT siblings of a core the same priority Ricardo Neri
2022-11-22 20:35 ` [PATCH v2 7/7] x86/sched/itmt: Consider the idle state of SMT siblings Ricardo Neri
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=xhsmhr0wre5rg.mognet@vschneid.remote.csb \
--to=vschneid@redhat.com \
--cc=bristot@redhat.com \
--cc=bsegall@google.com \
--cc=dietmar.eggemann@arm.com \
--cc=ionela.voinescu@arm.com \
--cc=juri.lelli@redhat.com \
--cc=len.brown@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mgorman@suse.de \
--cc=peterz@infradead.org \
--cc=rafael.j.wysocki@intel.com \
--cc=ravi.v.shankar@intel.com \
--cc=ricardo.neri-calderon@linux.intel.com \
--cc=ricardo.neri@intel.com \
--cc=rostedt@goodmis.org \
--cc=srinivas.pandruvada@linux.intel.com \
--cc=tim.c.chen@intel.com \
--cc=tim.c.chen@linux.intel.com \
--cc=vincent.guittot@linaro.org \
--cc=x86@kernel.org \
/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).