From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Joel Fernandes <joel@joelfernandes.org>,
"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>,
Naresh Kamboju <naresh.kamboju@linaro.org>,
William Kucharski <william.kucharski@oracle.com>
Subject: Re: [PATCHv2] mm: Fix warning in move_normal_pmd()
Date: Thu, 16 Jul 2020 16:16:12 +0300 [thread overview]
Message-ID: <20200716131612.b7ottczdgnxwdvrp@box> (raw)
In-Reply-To: <CAHk-=wjw2yuQjP1rqB=ocr9W3=ak+6h4XygoFTAgM5meiM1Q0A@mail.gmail.com>
On Wed, Jul 15, 2020 at 04:18:44PM -0700, Linus Torvalds wrote:
> On Wed, Jul 15, 2020 at 4:04 PM Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
> >
> > It *might* be as simple as this incremental thing on top
>
> No, it needs to be
>
> + if (*old_addr + *len < old->vm_end)
> + return;
>
> in try_to_align_end(), of course.
Okay, this should work, but I'm not convinced that it gives much: number
of cases covered by the optimization not going to be high.
It can also lead to performance regression: for small mremap() if only one
side of the range got aligned and there's no PMD_SIZE range to move,
kernel will still iterate over PTEs, but it would need to handle more
pte_none()s than without the patch.
--
Kirill A. Shutemov
next prev parent reply other threads:[~2020-07-16 13:16 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-15 13:50 Kirill A. Shutemov
2020-07-15 18:36 ` Linus Torvalds
2020-07-15 20:54 ` Joel Fernandes
2020-07-15 21:13 ` Kirill A. Shutemov
2020-07-15 21:31 ` Linus Torvalds
2020-07-15 21:43 ` Linus Torvalds
2020-07-15 22:22 ` Kirill A. Shutemov
2020-07-15 22:36 ` Linus Torvalds
2020-07-15 22:57 ` Linus Torvalds
2020-07-15 23:04 ` Linus Torvalds
2020-07-15 23:18 ` Linus Torvalds
2020-07-16 6:37 ` Naresh Kamboju
2020-07-16 7:23 ` Naresh Kamboju
2020-07-16 8:46 ` Kirill A. Shutemov
2020-07-16 8:32 ` Naresh Kamboju
2020-07-16 13:16 ` Kirill A. Shutemov [this message]
2020-07-16 17:54 ` Linus Torvalds
2020-07-16 18:47 ` Joel Fernandes
2020-07-15 20:55 ` Kirill A. Shutemov
2020-07-15 21:35 ` Linus Torvalds
2020-07-15 21:51 ` Linus Torvalds
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