Messages in this thread | | | Subject | Re: ** POTENTIAL FRAUD ALERT - RED HAT ** RE: [PATCH 0/3] mm/page_reporting: Make page reporting work on arm64 with 64KB page size | From | Gavin Shan <> | Date | Tue, 22 Jun 2021 12:04:49 +1000 |
| |
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
> >> 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 >>>
| |