From: Rik van Riel <riel@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Ebru Akagunduz <ebru.akagunduz@gmail.com>,
linux-mm@kvack.org, kirill@shutemov.name, mhocko@suse.cz,
mgorman@suse.de, rientjes@google.com, sasha.levin@oracle.com,
hughd@google.com, hannes@cmpxchg.org, vbabka@suse.cz,
linux-kernel@vger.kernel.org, aarcange@redhat.com,
keithr@alum.mit.edu, dvyukov@google.com
Subject: Re: [PATCH v2] mm: incorporate zero pages into transparent huge pages
Date: Mon, 23 Feb 2015 14:43:12 -0500 [thread overview]
Message-ID: <54EB82D0.9080606@redhat.com> (raw)
In-Reply-To: <20150223111621.bc73004f51af2ca8e2847944@linux-foundation.org>
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
On 02/23/2015 02:16 PM, Andrew Morton wrote:
> On Wed, 18 Feb 2015 19:08:12 -0500 Rik van Riel <riel@redhat.com>
> wrote:
>>> If so, this might be rather undesirable behaviour in some
>>> situations (and ditto the current behaviour for pte_none
>>> ptes)?
>>>
>>> This can be tuned by adjusting khugepaged_max_ptes_none,
> Here's a live one:
> https://bugzilla.kernel.org/show_bug.cgi?id=93111
>
> Application does MADV_DONTNEED to free up a load of memory and
> then khugepaged comes along and pages that memory back in again.
> It seems a bit silly to do this after userspace has deliberately
> discarded those pages!
>
> Presumably MADV_NOHUGEPAGE can be used to prevent this, but it's a
> bit of a hand-grenade. I guess the MADV_DONTNEED manpage should be
> updated to explain all this?
That makes me wonder what a good value for khugepaged_max_ptes_none
would be.
Doubling the amount of memory a program uses seems quite unreasonable.
Increasing the amount of memory a program uses by 512x seems totally
unreasonable.
Increasing the amount of memory a program uses by 20% might be
reasonable, if that much memory is available, since that seems to
be about how much performance improvement we have ever seen from
THP.
Andrew, Andrea, do you have any ideas on this?
Is this something to just set, or should we ask Ebru to run
a few different tests with this?
- --
All rights reversed
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
iQEcBAEBAgAGBQJU64LQAAoJEM553pKExN6DbjAH/31KsggMczFT5Z6KQ68dnMnc
nlYAHmiC8nBzguhj5fUtm94jWBK1IPg9cUkRt1tKDJXkVGk91it0MdO1QhuSL91b
xNghqc1d8/P/dmuguNH6C7BUlf52iFFyaCrnip+sO1rxIEUYkFwHxpwC5vSlLrrl
bENlILFuY5kmF2xd6kIfvhOr7TzkbCS92Da3la0sCIT4tjlXPKJ6fuTo9aK8LOqr
kKi6gmmyH+gDhi2EAJk3D1cZT8RqrynsbirEEcWq+ORNUScmSqNlQqGOLw/nJeSp
Nkw7rReeMz5PHVxnsNQE4kxQ4zIJ0auZsZ9cC4Gw3ZpQKdiLBiAK+lJECgQsqPk=
=pDxP
-----END PGP SIGNATURE-----
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2015-02-23 20:24 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-11 21:03 Ebru Akagunduz
2015-02-11 22:16 ` Andrea Arcangeli
2015-02-11 22:21 ` Kirill A. Shutemov
2015-02-11 22:33 ` Andrea Arcangeli
2015-02-16 11:50 ` Vlastimil Babka
2015-02-18 23:31 ` Andrew Morton
2015-02-19 0:08 ` Rik van Riel
2015-02-19 8:25 ` Vlastimil Babka
2015-02-23 19:16 ` Andrew Morton
2015-02-23 19:43 ` Rik van Riel [this message]
2015-02-23 21:45 ` Vlastimil Babka
2015-02-20 18:02 ` Andrea Arcangeli
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=54EB82D0.9080606@redhat.com \
--to=riel@redhat.com \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=dvyukov@google.com \
--cc=ebru.akagunduz@gmail.com \
--cc=hannes@cmpxchg.org \
--cc=hughd@google.com \
--cc=keithr@alum.mit.edu \
--cc=kirill@shutemov.name \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@suse.de \
--cc=mhocko@suse.cz \
--cc=rientjes@google.com \
--cc=sasha.levin@oracle.com \
--cc=vbabka@suse.cz \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox