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

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Message-ID: <383084c1-370d-4cda-8d5d-01f7da827b50@amd.com>
Date: Fri, 11 Jul 2025 11:22:39 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: Li Chen <me@...ux.beauty>, 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: Re: [PATCH v5 0/4] x86/smpboot: tidy sched-topology and drop useless
 SMT level

Hello Li,

On 7/10/2025 4:27 PM, Li Chen wrote:
> 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.

Feel free to include:

Reviewed-by: K Prateek Nayak <kprateek.nayak@....com>

I've given this series a spin again when looking at "tl->flags"
and everything runs as expected on x86 :)

> 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(-)
> 

-- 
Thanks and Regards,
Prateek