linux-kernel - Re: [PATCH V13 4/4] LoongArch: Enable ARCH_WANT_HUGETLB_PAGE_OPTIMIZE

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Date:   Wed, 26 Oct 2022 15:44:25 +0200
From:   Philippe Mathieu-Daudé <philmd@...aro.org>
To:     Huacai Chen <chenhuacai@...nel.org>, Guo Ren <guoren@...nel.org>
Cc:     Huacai Chen <chenhuacai@...ngson.cn>,
        Arnd Bergmann <arnd@...db.de>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Dinh Nguyen <dinguyen@...nel.org>, loongarch@...ts.linux.dev,
        linux-arch@...r.kernel.org, Xuefeng Li <lixuefeng@...ngson.cn>,
        Xuerui Wang <kernel@...0n.name>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Feiyang Chen <chenfeiyang@...ngson.cn>
Subject: Re: [PATCH V13 4/4] LoongArch: Enable
 ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP

On 26/10/22 14:59, Huacai Chen wrote:
> On Mon, Oct 24, 2022 at 4:04 PM Guo Ren <guoren@...nel.org> wrote:
>> On Mon, Oct 24, 2022 at 3:05 PM Huacai Chen <chenhuacai@...ngson.cn> wrote:
>>>
>>> From: Feiyang Chen <chenfeiyang@...ngson.cn>
>>>
>>> The feature of minimizing overhead of struct page associated with each
>>> HugeTLB page is implemented on x86_64. However, the infrastructure of
>>> this feature is already there, so just select ARCH_WANT_HUGETLB_PAGE_
>>> OPTIMIZE_VMEMMAP is enough to enable this feature for LoongArch.
>>>
>>> To avoid the following build error on LoongArch we should include linux/
>>> static_key.h in page-flags.h. This is straightforward but the build
>>> error is implicitly a LoongArch-specific problem, because ARM64 and X86
>>> have already include static_key.h from their arch-specific core headers.

>>> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
>>> index 0b0ae5084e60..1aafdc73e399 100644
>>> --- a/include/linux/page-flags.h
>>> +++ b/include/linux/page-flags.h
>>> @@ -9,6 +9,7 @@
>>>   #include <linux/types.h>
>>>   #include <linux/bug.h>
>>>   #include <linux/mmdebug.h>
>>> +#include <linux/static_key.h>
>> Em... riscv needn't this.

Would guarding the header suffice and make riscv OK with this patch?

  #ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
  #include <linux/static_key.h>
  #endif

> I found that after 36d4b36b69590fed99356a4426c940a25 (" lib/nodemask:
> inline next_node_in() and node_random()"), build errors have gone. But
> I think this is just an accident. Because that commit adds random.h
> inclusion in nodemask.h, then asm-offsets.c --> sched.h --> nodemask.h
> --> random.h --> once.h --> jump_label.h. If one day this chain is
> adjusted, then build errors come again.
> 
> On the other hand, page-flags.h is obviously using some static_key
> macros, including static_key.h is straightforward for building.
> 
> Huacai