From: Zi Yan <ziy@nvidia.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: David Hildenbrand <david@redhat.com>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org, linux-mm@kvack.org,
iommu@lists.linux-foundation.org,
Robin Murphy <robin.murphy@arm.com>,
Christoph Hellwig <hch@lst.de>,
Marek Szyprowski <m.szyprowski@samsung.com>
Subject: Re: [RFC PATCH 0/3] Use pageblock_order for cma and alloc_contig_range alignment.
Date: Fri, 19 Nov 2021 10:15:40 -0500 [thread overview]
Message-ID: <AEFF28CF-0ED8-450F-96A4-A6CD59CB1F3D@nvidia.com> (raw)
In-Reply-To: <3083463d-978b-fbe6-dadf-670d400ed437@suse.cz>
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On 19 Nov 2021, at 7:33, Vlastimil Babka wrote:
> On 11/15/21 20:37, Zi Yan wrote:
>> From: Zi Yan <ziy@nvidia.com>
>>
>> Hi David,
>>
>> You suggested to make alloc_contig_range() deal with pageblock_order instead of
>> MAX_ORDER - 1 and get rid of MAX_ORDER - 1 dependency in virtio_mem[1]. This
>> patchset is my attempt to achieve that. Please take a look and let me know if
>> I am doing it correctly or not.
>>
>> From what my understanding, cma required alignment of
>> max(MAX_ORDER - 1, pageblock_order), because when MIGRATE_CMA was introduced,
>> __free_one_page() does not prevent merging two different pageblocks, when
>> MAX_ORDER - 1 > pageblock_order. But current __free_one_page() implementation
>> does prevent that.
>
> But it does prevent that only for isolated pageblock, not CMA, and yout
> patchset doesn't seem to expand that to CMA? Or am I missing something.
Yeah, you are right. Originally, I thought preventing merging isolated pageblock
with other types of pageblocks is sufficient, since MIGRATE_CMA is always
converted from MIGRATE_ISOLATE. But that is not true. I will rework the code.
Thanks for pointing this out.
>
>
>> It should be OK to just align cma to pageblock_order.
>> alloc_contig_range() relies on MIGRATE_CMA to get free pages, so it can use
>> pageblock_order as alignment too.
>>
>> In terms of virtio_mem, if I understand correctly, it relies on
>> alloc_contig_range() to obtain contiguous free pages and offlines them to reduce
>> guest memory size. As the result of alloc_contig_range() alignment change,
>> virtio_mem should be able to just align PFNs to pageblock_order.
>>
>> Thanks.
>>
>>
>> [1] https://lore.kernel.org/linux-mm/28b57903-fae6-47ac-7e1b-a1dd41421349@redhat.com/
>>
>> Zi Yan (3):
>> mm: cma: alloc_contig_range: use pageblock_order as the single
>> alignment.
>> drivers: virtio_mem: use pageblock size as the minimum virtio_mem
>> size.
>> arch: powerpc: adjust fadump alignment to be pageblock aligned.
>>
>> arch/powerpc/include/asm/fadump-internal.h | 4 +---
>> drivers/virtio/virtio_mem.c | 6 ++----
>> include/linux/mmzone.h | 5 +----
>> kernel/dma/contiguous.c | 2 +-
>> mm/cma.c | 6 ++----
>> mm/page_alloc.c | 12 +++++-------
>> 6 files changed, 12 insertions(+), 23 deletions(-)
>>
--
Best Regards,
Yan, Zi
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next prev parent reply other threads:[~2021-11-19 15:17 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-15 19:37 [RFC PATCH 0/3] Use pageblock_order for cma and alloc_contig_range alignment Zi Yan
2021-11-15 19:37 ` [RFC PATCH 1/3] mm: cma: alloc_contig_range: use pageblock_order as the single alignment Zi Yan
2021-11-15 19:37 ` [RFC PATCH 2/3] drivers: virtio_mem: use pageblock size as the minimum virtio_mem size Zi Yan
2021-11-15 19:37 ` [RFC PATCH 3/3] arch: powerpc: adjust fadump alignment to be pageblock aligned Zi Yan
2021-11-15 19:37 ` [RFC PATCH 3/3] arch: powerpc: adjust fadump alignment to " Zi Yan
2021-11-16 8:58 ` [RFC PATCH 0/3] Use pageblock_order for cma and alloc_contig_range alignment David Hildenbrand
2021-11-17 3:04 ` Zi Yan
2021-11-23 16:54 ` David Hildenbrand
2021-11-19 12:33 ` Vlastimil Babka
2021-11-19 15:15 ` Zi Yan [this message]
2021-11-23 16:35 ` Zi Yan
2021-11-23 17:32 ` Vlastimil Babka
2021-11-29 22:08 ` Zi Yan
2021-11-30 9:11 ` Vlastimil Babka
2021-11-30 10:08 ` Mel Gorman
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