From: Valentin Schneider <valentin.schneider@arm.com>
To: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
morten.rasmussen@arm.com, qperret@google.com,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>
Subject: [PATCH 2/2] arm64: defconfig: enable CONFIG_SCHED_SMT
Date: Wed, 26 Feb 2020 16:41:18 +0000 [thread overview]
Message-ID: <20200226164118.6405-3-valentin.schneider@arm.com> (raw)
In-Reply-To: <20200226164118.6405-1-valentin.schneider@arm.com>
The (CFS) scheduler has some extra logic catering to systems with SMT, but
that logic won't be compiled in unless the above config is set.
Note that the SMT-centric codepaths are gated by the sched_smt_present
static key, and the SMT sched_domains will only survive if the platform has
SMT. As such, the only impact on !SMT platforms should be a slightly
bigger kernel - no behavioural change.
Distro kernels already enable it, which makes sense since there already are
things like ThunderX2 out in the wild. Enable it for the defconfig.
Some deltas
===========
FWIW my ELF symbol table diff looks something like this:
NAME BEFORE AFTER DELTA
update_sd_lb_stats.constprop.135 0 1864 +1864
find_idlest_group.isra.115 0 1808 +1808
update_numa_stats.isra.121 0 628 +628
select_task_rq_fair 3236 3732 +496
compute_energy.isra.112 0 420 +420
score_nearby_nodes.part.120 0 380 +380
__update_idle_core 0 232 +232
nohz_balance_exit_idle.part.127 0 216 +216
sched_slice.isra.99 0 172 +172
update_load_avg.part.107 0 116 +116
wakeup_preempt_entity.isra.101 0 92 +92
sched_cpu_activate 340 396 +56
pick_next_task_idle 8 56 +48
sched_cpu_deactivate 252 292 +40
show_smt_active 44 80 +36
cpu_smt_mask 0 28 +28
set_next_task_idle 4 32 +28
task_numa_work 680 692 +12
cpu_smt_flags 0 8 +8
enqueue_task_fair 2608 2612 +4
wakeup_preempt_entity.isra.104 92 0 -92
update_load_avg 1028 932 -96
task_numa_migrate 1824 1728 -96
sched_slice.isra.102 172 0 -172
nohz_balance_exit_idle.part.130 216 0 -216
task_numa_find_cpu 2116 1868 -248
score_nearby_nodes.part.123 380 0 -380
compute_energy.isra.115 420 0 -420
update_numa_stats.isra.124 472 0 -472
find_idlest_group.isra.118 1808 0 -1808
update_sd_lb_stats.constprop.138 1864 0 -1864
------------------------------------------------------------------
DELTA SUM +820
As for the sched_domains, this is on a hikey960:
before:
$ cat /proc/sys/kernel/sched_domain/cpu*/domain*/name | sort | uniq
DIE
MC
after:
$ cat /proc/sys/kernel/sched_domain/cpu*/domain*/name | sort | uniq
DIE
MC
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
---
arch/arm64/configs/defconfig | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/arm64/configs/defconfig b/arch/arm64/configs/defconfig
index 905109f6814f..3e75007f6592 100644
--- a/arch/arm64/configs/defconfig
+++ b/arch/arm64/configs/defconfig
@@ -62,6 +62,7 @@ CONFIG_ARCH_ZX=y
CONFIG_ARCH_ZYNQMP=y
CONFIG_ARM64_VA_BITS_48=y
CONFIG_SCHED_MC=y
+CONFIG_SCHED_SMT=y
CONFIG_NUMA=y
CONFIG_SECCOMP=y
CONFIG_KEXEC=y
--
2.24.0
next prev parent reply other threads:[~2020-02-26 16:42 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-26 16:41 [PATCH 0/2] sched, arm64: enable CONFIG_SCHED_SMT for arm64 Valentin Schneider
2020-02-26 16:41 ` [PATCH 1/2] sched/topology: Don't enable EAS on SMT systems Valentin Schneider
2020-02-27 13:00 ` Quentin Perret
2020-02-27 16:28 ` Dietmar Eggemann
2020-02-27 16:42 ` Valentin Schneider
2020-02-26 16:41 ` Valentin Schneider [this message]
2020-02-27 16:32 ` [PATCH 0/2] sched, arm64: enable CONFIG_SCHED_SMT for arm64 Dietmar Eggemann
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=20200226164118.6405-3-valentin.schneider@arm.com \
--to=valentin.schneider@arm.com \
--cc=catalin.marinas@arm.com \
--cc=dietmar.eggemann@arm.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=mingo@kernel.org \
--cc=morten.rasmussen@arm.com \
--cc=peterz@infradead.org \
--cc=qperret@google.com \
--cc=vincent.guittot@linaro.org \
--cc=will@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
all inboxes | Powered by JetHome®