linux-kernel - Re: [PATCH RFC 0/4] mm: percpu: Cleanup percpu first chunk funciton

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Message-ID: <YaVaTwjiZmWz8PKY@fedora>
Date:   Mon, 29 Nov 2021 17:55:11 -0500
From:   Dennis Zhou <dennis@...nel.org>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>
Cc:     akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, tj@...nel.org, gregkh@...uxfoundation.org,
        cl@...ux.com, catalin.marinas@....com, will@...nel.org,
        tsbogend@...ha.franken.de, mpe@...erman.id.au,
        benh@...nel.crashing.org, paulus@...ba.org,
        paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, davem@...emloft.net, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        hpa@...or.com, linux-arm-kernel@...ts.infradead.org,
        linux-ia64@...r.kernel.org, linux-mips@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
        sparclinux@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH RFC 0/4] mm: percpu: Cleanup percpu first chunk funciton

Hello,

On Sun, Nov 21, 2021 at 05:35:53PM +0800, Kefeng Wang wrote:
> When support page mapping percpu first chunk allocator on arm64, we
> found there are lots of duplicated codes in percpu embed/page first
> chunk allocator. This patchset is aimed to cleanup them and should
> no funciton change, only test on arm64.
> 
> Kefeng Wang (4):
>   mm: percpu: Generalize percpu related config
>   mm: percpu: Add pcpu_fc_cpu_to_node_fn_t typedef
>   mm: percpu: Add generic pcpu_fc_alloc/free funciton
>   mm: percpu: Add generic pcpu_populate_pte() function
> 
>  arch/arm64/Kconfig             |  20 +----
>  arch/ia64/Kconfig              |   9 +--
>  arch/mips/Kconfig              |  10 +--
>  arch/mips/mm/init.c            |  14 +---
>  arch/powerpc/Kconfig           |  17 +---
>  arch/powerpc/kernel/setup_64.c |  92 +--------------------
>  arch/riscv/Kconfig             |  10 +--
>  arch/sparc/Kconfig             |  12 +--
>  arch/sparc/kernel/smp_64.c     | 105 +-----------------------
>  arch/x86/Kconfig               |  17 +---
>  arch/x86/kernel/setup_percpu.c |  66 ++-------------
>  drivers/base/arch_numa.c       |  68 +---------------
>  include/linux/percpu.h         |  13 +--
>  mm/Kconfig                     |  12 +++
>  mm/percpu.c                    | 143 +++++++++++++++++++++++++--------
>  15 files changed, 165 insertions(+), 443 deletions(-)
> 
> -- 
> 2.26.2
> 

I've made a few comments. I think this will be a little bit of a
challenge to get through due to it touching so many architectures. For
ease, it probably makes sense to run it through mny tree, but we'll need
explicit acks as I mentioned.

I like getting rid of the pcpu_alloc_bootmem()/pcpu_free_bootmem()
functions. However, let's keep the implementation identical to x86.


I don't think we should get rid of the populate_pte_fn(). I'm not
comfortable changing x86's implementation. Simply offer a NULL, and if
NULL use the default.

Do you have a tree that intel pulls? I suggest cleaning up the patches
and pushing to a remote branch that they pick up. That would have caught
the mips typo. Send a PR creating a file in [1] for your branch, github
is fine. Basic validation needs to be done before I can pick this up
too on more than arm64.

[1] https://github.com/intel/lkp-tests/tree/master/repo/linux

Thanks,
Dennis