linux-kernel - [PATCH v5 0/4] x86/smpboot: tidy sched-topology and drop useless SMT level

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Message-ID: <20250710105715.66594-1-me@linux.beauty>
Date: Thu, 10 Jul 2025 18:57:06 +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>,
	"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 v5 0/4] x86/smpboot: tidy sched-topology and drop useless SMT level

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

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

Patch 1, 2, and 3 do some cleanup and refactor.

Patch 4 is a follow-up that simply skip SMT domain when
cpu_smt_num_threads <= 1, so the SMT level never gets created.

Tested on Qemu.

changelog:
v2: fix wording issue as suggested by Thomas [1]
v3: remove pointless memset and adjust PKG index accordingly, as
    suggested by Thomas [2], and refine some other wording issues.
v4: v4: Split refactor patche into three parts (as suggested by Peter [3])
    and refined patch 4 logic (as done by K. [4]).
v5: fix some style issues and do some improvements as pointed out by K. [5][6]

[1]: https://lore.kernel.org/all/87msa2r018.ffs@tglx/
[2]: https://lore.kernel.org/all/875xglntx1.ffs@tglx/
[3]: https://lkml.org/lkml/2025/6/25/584
[4]: https://lore.kernel.org/lkml/1b706790-2fec-4582-a425-55eeff36c32e@amd.com/
[5]: https://lore.kernel.org/all/f391491d-f886-4579-9b40-78a57f2ed1b5@amd.com/
[6]: https://lore.kernel.org/all/7e7f686b-1f5a-46dc-8b16-c6d491160d1c@amd.com/

Li Chen (4):
  smpboot: introduce SDTL() helper to tidy sched topology setup
  x86/smpboot: remove redundant CONFIG_SCHED_SMT
  x86/smpboot: moves x86_topology to static initialize and truncate
  x86/smpboot: avoid SMT domain attach/destroy if SMT is not enabled

 arch/powerpc/kernel/smp.c      | 34 +++++++++--------------
 arch/s390/kernel/topology.c    | 10 +++----
 arch/x86/kernel/smpboot.c      | 51 ++++++++++++++++------------------
 include/linux/sched/topology.h |  4 +--
 kernel/sched/topology.c        | 24 ++++++----------
 5 files changed, 52 insertions(+), 71 deletions(-)

-- 
2.50.0