linux-kernel - Re: [PATCH v3 2/4] mm: Default implementation of arch_wants_pte

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAOUHufZ7HJZW8Srwatyudf=FbwTGQtyq4DyL2SHwSg37N_Bo_A@mail.gmail.com>
Date:   Fri, 14 Jul 2023 10:54:20 -0600
From:   Yu Zhao <yuzhao@...gle.com>
To:     Ryan Roberts <ryan.roberts@....com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Yin Fengwei <fengwei.yin@...el.com>,
        David Hildenbrand <david@...hat.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Yang Shi <shy828301@...il.com>,
        "Huang, Ying" <ying.huang@...el.com>, Zi Yan <ziy@...dia.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH v3 2/4] mm: Default implementation of arch_wants_pte_order()

On Fri, Jul 14, 2023 at 10:17 AM Ryan Roberts <ryan.roberts@....com> wrote:
>
> arch_wants_pte_order() can be overridden by the arch to return the
> preferred folio order for pte-mapped memory. This is useful as some
> architectures (e.g. arm64) can coalesce TLB entries when the physical
> memory is suitably contiguous.
>
> The first user for this hint will be FLEXIBLE_THP, which aims to
> allocate large folios for anonymous memory to reduce page faults and
> other per-page operation costs.
>
> Here we add the default implementation of the function, used when the
> architecture does not define it, which returns -1, implying that the HW
> has no preference. In this case, mm will choose it's own default order.
>
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>

Reviewed-by: Yu Zhao <yuzhao@...gle.com>

Thanks: -1 actually is better than 0 (what I suggested) for the obvious reason.