linux-kernel - Re: [PATCH v3 bpf RESEND 2/4] page_alloc: use __vmalloc

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Message-ID: <030EA68F-EAA1-41C8-B7FA-0675B118F0D8@fb.com>
Date:   Fri, 15 Apr 2022 16:57:01 +0000
From:   Song Liu <songliubraving@...com>
To:     Christoph Hellwig <hch@...radead.org>
CC:     Song Liu <song@...nel.org>, bpf <bpf@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        open list <linux-kernel@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <Kernel-team@...com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "rick.p.edgecombe@...el.com" <rick.p.edgecombe@...el.com>,
        "imbrenda@...ux.ibm.com" <imbrenda@...ux.ibm.com>,
        "mcgrof@...nel.org" <mcgrof@...nel.org>
Subject: Re: [PATCH v3 bpf RESEND 2/4] page_alloc: use __vmalloc_huge for
 large system hash

Hi Christoph, 

> On Apr 14, 2022, at 11:32 PM, Christoph Hellwig <hch@...radead.org> wrote:
> 
> On Thu, Apr 14, 2022 at 12:59:12PM -0700, Song Liu wrote:
>> Use __vmalloc_huge() in alloc_large_system_hash() so that large system
>> hash (>= PMD_SIZE) could benefit from huge pages. Note that __vmalloc_huge
>> only allocates huge pages for systems with HAVE_ARCH_HUGE_VMALLOC.
> 
> Looks good (modulo the possible naming chane suggested in patch 1):
> 
> Reviewed-by: Christoph Hellwig <hch@....de>

Thanks for your kind review!

Could you please share your thoughts on shipping the set with 5.18 (or 
whether we should postpone it)? 

AFAICT, the only changed behavior is to allow alloc_large_system_hash
return huge pages for size > PMD_SIZE on x86_64. I think this is 
relatively safe, as this is only for large hash and we are at rc2. 

Thanks,
Song