netdev - Re: [PATCH bpf 3/4] x86: select HAVE_ARCH_HUGE_VMALLOC_FLAG for X86

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Date:   Thu, 31 Mar 2022 00:30:39 +0000
From:   Song Liu <songliubraving@...com>
To:     Thomas Gleixner <tglx@...utronix.de>
CC:     Song Liu <song@...nel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "andrii@...nel.org" <andrii@...nel.org>,
        Kernel Team <Kernel-team@...com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "pmenzel@...gen.mpg.de" <pmenzel@...gen.mpg.de>,
        "rick.p.edgecombe@...el.com" <rick.p.edgecombe@...el.com>
Subject: Re: [PATCH bpf 3/4] x86: select HAVE_ARCH_HUGE_VMALLOC_FLAG for
 X86_64



> On Mar 30, 2022, at 4:54 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> 
> On Wed, Mar 30 2022 at 15:56, Song Liu wrote:
>> As HAVE_ARCH_HUGE_VMALLOC is not ready for X86_64, enable
>> HAVE_ARCH_HUGE_VMALLOC_FLAG to allow bpf_prog_pack to allocate huge
>> pages.
> 
> Despite HAVE_ARCH_HUGE_VMALLOC being not ready for X86_64 enable it
> nevertheless?

These are two different flags:

HAVE_ARCH_HUGE_VMALLOC allows vmalloc to try to allocate huge pages for
size >= PMD_SIZE, unless it is disabled with nohugeiomap or VM_NO_HUGE_VMAP.

HAVE_ARCH_HUGE_VMALLOC_FLAG allows vmalloc to try to allocate huge pages
for size >= PMD_SIZE, only when the user specifies VM_TRY_HUGE_VMAP. 

Recommendations for better naming will be highly appreciated..

Song


> 
> I assume you wanted to say something like this:
> 
>  The shortcomings of huge vmalloc allocations have been fixed in the
>  memory management core code, so reenable HAVE_ARCH_HUGE_VMALLOC.
> 
> Thanks,
> 
>        tglx