linux-kernel - [PATCH V2 0/2] x86/smpboot: tidy sched-topology and drop useless SMT level

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Message-ID: <20250624085559.69436-1-me@linux.beauty>
Date: Tue, 24 Jun 2025 16:55:55 +0800
From: Li Chen <me@...ux.beauty>
To: Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H . Peter Anvin" <hpa@...or.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	K Prateek Nayak <kprateek.nayak@....com>,
	Sohil Mehta <sohil.mehta@...el.com>,
	Brian Gerst <brgerst@...il.com>,
	Patryk Wlazlyn <patryk.wlazlyn@...ux.intel.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH V2 0/2] x86/smpboot: tidy sched-topology and drop useless SMT level

From: Li Chen <chenl311@...natelecom.cn>

This two–patch series cleans up sched-domain topology handling and
eliminates hundreds of pointless attach/destroy cycles when SMT is
not available.

Patch 1  (from Thomas, unchanged) gets rid of the #ifdef maze in
build_sched_topology() by statically initialising the topology array.

Patch 2  (mine) is a follow-up that simply memmoves the array when
cpu_smt_num_threads <= 1, so the SMT level never gets created and
immediately torn down again.

Tested on Qemu.

changelog:
v2: fix wording issue as suggested by Thomas [1]

[1]: https://www.spinics.net/lists/kernel/msg5732082.html

Li Chen (1):
  x86/smpboot: avoid SMT domain attach/destroy if SMT is not enabled

Thomas Gleixner (1):
  x86/smpboot: Decrapify build_sched_topology()

 arch/x86/kernel/smpboot.c | 59 +++++++++++++++++++++------------------
 1 file changed, 32 insertions(+), 27 deletions(-)

-- 
2.49.0