From: Dan Williams <dan.j.williams@intel.com>
To: yang.shi@linux.alibaba.com
Cc: Jan Kara <jack@suse.cz>,
Ross Zwisler <ross.zwisler@linux.intel.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linux MM <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm: enforce THP for VM_NOHUGEPAGE dax mappings
Date: Fri, 28 Sep 2018 15:36:49 -0700 [thread overview]
Message-ID: <CAPcyv4jdTWoJMSPuxso=8fu8nGOrmbBPYxkJvsuEDfJSYvsDWg@mail.gmail.com> (raw)
In-Reply-To: <1538173916-95849-1-git-send-email-yang.shi@linux.alibaba.com>
On Fri, Sep 28, 2018 at 3:34 PM <yang.shi@linux.alibaba.com> wrote:
>
> commit baabda261424517110ea98c6651f632ebf2561e3 ("mm: always enable thp
> for dax mappings") says madvise hguepage policy makes less sense for
> dax, and force enabling thp for dax mappings in all cases, even though
> THP is set to "never".
>
> However, transparent_hugepage_enabled() may return false if
> VM_NOHUGEPAGE is set even though the mapping is dax.
>
> So, move is_vma_dax() check to the very beginning to enforce THP for dax
> mappings in all cases.
>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
> Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
> ---
> I didn't find anyone mention the check should be before VM_NOHUGEPAGE in
> the review for Dan's original patch. And, that patch commit log states
> clearly that THP for dax mapping for all cases even though THP is never.
> So, I'm supposed it should behave in this way.
No, if someone explicitly does MADV_NOHUGEPAGE then the kernel should
honor that, even if the mapping is DAX.
next prev parent reply other threads:[~2018-09-28 22:37 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-28 22:31 Yang Shi
2018-09-28 22:36 ` Dan Williams [this message]
2018-09-28 22:43 ` Yang Shi
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