From: Michael Kelley <mikelley@microsoft.com>
To: Gavin Shan <gshan@redhat.com>,
Alexander Duyck <alexander.duyck@gmail.com>
Cc: linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@redhat.com>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
"shan.gavin@gmail.com" <shan.gavin@gmail.com>
Subject: RE: [PATCH 0/3] mm/page_reporting: Make page reporting work on arm64 with 64KB page size
Date: Tue, 22 Jun 2021 23:25:06 +0000 [thread overview]
Message-ID: <MWHPR21MB1593D17E79F4FFBB4A36F32BD7099@MWHPR21MB1593.namprd21.prod.outlook.com> (raw)
From: Gavin Shan <gshan@redhat.com> Sent: Monday, June 21, 2021 7:05 PM
>
> On 6/22/21 2:06 AM, Michael Kelley wrote:
> > From: Alexander Duyck <alexander.duyck@gmail.com> Sent: Monday, June 21, 2021 7:02
> AM
> >> To: Gavin Shan <gshan@redhat.com>
> >> Cc: linux-mm <linux-mm@kvack.org>; LKML <linux-kernel@vger.kernel.org>; Andrew
> >> Morton <akpm@linux-foundation.org>; David Hildenbrand <david@redhat.com>;
> >> Anshuman Khandual <anshuman.khandual@arm.com>; Catalin Marinas
> >> <catalin.marinas@arm.com>; Will Deacon <will@kernel.org>; shan.gavin@gmail.com
> >> Subject: Re: [PATCH 0/3] mm/page_reporting: Make page reporting work on arm64 with
> >> 64KB page size
> >>
> >> So the question I would have is what is the use case for this? It
> >> seems like you don't have to deal with the guest native page size
> >> issues since you are willing to break up what would otherwise be THP
> >> pages on the guest, and the fact that you are willing to go down to
> >> 2MB pages which happens to align with the host THP page size for x86
> >> makes me wonder if that is actually the environment you are running
> >> in.
> >>
> >> Rather than having the guest control this it might make sense to look
> >> at adding an interface so that the page_reporting_register function
> >> and the page_reporting_dev_info struct could be used to report and
> >> configure the minimum page size that the host can support for the page
> >> reporting. With that the host could then guarantee that it isn't going
> >> to hurt performance by splitting pages on the host and risk hurting
> >> the virtualization performance.
> >>
> >> Also you would benefit by looking into the callers of
> >> page_reporting_register as there are more than just the virtio balloon
> >> that are consuming it. Odds are HyperV won't care about an ARM64
> >> architecture,
> >
> > FWIW, Hyper-V *does* care about ARM64. It's already in use by
> > the Windows Subsystem for Linux VM that's part of Windows 10
> > on ARM64 hardware. We're working to get the code accepted
> > upstream.
> >
>
> Michael, thanks for your confirmation. As the issue found on 64KB guest
> when memory balloon is used, lets resolve the case first. I will look
> into Hyper-V case later if you agree. It won't be difficult to fix the
> same issue for Hyper-V after the solution is figured out for memory
> balloon.
>
> Thanks,
> Gavin
This should be fine. For reference, the Hyper-V ARM64 host always
runs with a base page size of 4K. Linux guests on Hyper-V may have base
page size of 4K, 16K, or 64K.
Michael
>
> >
> >> but your change would essentially disable it outright
> >> which is why I think this might be better to address via the consumers
> >> of page reporting rather than trying to address it in page reporting
> >> itself.
> >>
> >> Thanks,
> >>
> >> - Alex
> >>
> >> On Sun, Jun 20, 2021 at 8:11 PM Gavin Shan <gshan@redhat.com> wrote:
> >>>
> >>> The page reporting threshold is currently equal to @pageblock_order, which
> >>> is 13 and 512MB on arm64 with 64KB base page size selected. The page
> >>> reporting won't be triggered if the freeing page can't come up with a free
> >>> area like that huge. The condition is hard to be met, especially when the
> >>> system memory becomes fragmented.
> >>>
> >>> This series intends to solve the issue by having page reporting threshold
> >>> as 5 (2MB) on arm64 with 64KB base page size. The patches are organized as:
> >>>
> >>> PATCH[1/3] introduces variable (@page_reporting_order) to replace original
> >>> macro (PAGE_REPORTING_MIN_ORDER). It's also exported so that it
> >>> can be adjusted at runtime.
> >>> PATCH[2/3] renames PAGE_REPORTING_MIN_ORDER with
> PAGE_REPORTING_ORDER
> >> and
> >>> allows architecture to specify its own version.
> >>> PATCH[3/3] defines PAGE_REPORTING_ORDER to 5, corresponding to 2MB in size,
> >>> on arm64 when 64KB base page size is selected. It's still same
> >>> as to @pageblock_order for other architectures and cases.
> >>>
> >>> Gavin Shan (3):
> >>> mm/page_reporting: Allow to set reporting order
> >>> mm/page_reporting: Allow architecture to select reporting order
> >>> arm64: mm: Specify smaller page reporting order
> >>>
> >>> Documentation/admin-guide/kernel-parameters.txt | 6 ++++++
> >>> arch/arm64/include/asm/page.h | 13 +++++++++++++
> >>> mm/page_reporting.c | 8 ++++++--
> >>> mm/page_reporting.h | 10 +++++++---
> >>> 4 files changed, 32 insertions(+), 5 deletions(-)
> >>>
> >>> --
> >>> 2.23.0
> >>>
next reply other threads:[~2021-06-22 23:25 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-22 23:25 Michael Kelley [this message]
-- strict thread matches above, loose matches on Subject: below --
2021-06-21 5:11 [PATCH 0/3] mm/page_reporting: Make page reporting work on arm64 with 64KB page size Gavin Shan
2021-06-21 14:02 ` Alexander Duyck
2021-06-21 16:06 ` Michael Kelley
2021-06-22 2:01 ` Gavin Shan
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=MWHPR21MB1593D17E79F4FFBB4A36F32BD7099@MWHPR21MB1593.namprd21.prod.outlook.com \
--to=mikelley@microsoft.com \
--cc=akpm@linux-foundation.org \
--cc=alexander.duyck@gmail.com \
--cc=anshuman.khandual@arm.com \
--cc=catalin.marinas@arm.com \
--cc=david@redhat.com \
--cc=gshan@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=shan.gavin@gmail.com \
--cc=will@kernel.org \
/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;
as well as URLs for NNTP newsgroup(s).