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Message-ID: <ba3e3dfa-d019-4991-9e3a-d73ffa83bb36@linux.alibaba.com>
Date: Wed, 31 Jul 2024 18:22:17 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: Kefeng Wang <wangkefeng.wang@...wei.com>, Barry Song <21cnbao@...il.com>
Cc: akpm@...ux-foundation.org, hughd@...gle.com, willy@...radead.org,
david@...hat.com, ryan.roberts@....com, ziy@...dia.com, gshan@...hat.com,
ioworker0@...il.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] mm: shmem: avoid allocating huge pages larger than
MAX_PAGECACHE_ORDER for shmem
On 2024/7/31 17:59, Kefeng Wang wrote:
>
>
> On 2024/7/31 16:56, Baolin Wang wrote:
>>
>>
>> On 2024/7/31 14:18, Barry Song wrote:
>>> On Wed, Jul 31, 2024 at 1:46 PM Baolin Wang
>>> <baolin.wang@...ux.alibaba.com> wrote:
>>>>
>>>> Similar to commit d659b715e94ac ("mm/huge_memory: avoid PMD-size
>>>> page cache
>>>> if needed"), ARM64 can support 512MB PMD-sized THP when the base
>>>> page size is
>>>> 64KB, which is larger than the maximum supported page cache size
>>>> MAX_PAGECACHE_ORDER.
>>>> This is not expected. To fix this issue, use
>>>> THP_ORDERS_ALL_FILE_DEFAULT for
>>>> shmem to filter allowable huge orders.
>>>>
>>>> Fixes: e7a2ab7b3bb5 ("mm: shmem: add mTHP support for anonymous shmem")
>>>> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
>>>
>>> Reviewed-by: Barry Song <baohua@...nel.org>
>>
>> Thanks for reviewing.
>>
>>>
>>>> ---
>>>> mm/shmem.c | 4 ++--
>>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/mm/shmem.c b/mm/shmem.c
>>>> index 2faa9daaf54b..a4332a97558c 100644
>>>> --- a/mm/shmem.c
>>>> +++ b/mm/shmem.c
>>>> @@ -1630,10 +1630,10 @@ unsigned long
>>>> shmem_allowable_huge_orders(struct inode *inode,
>>>> unsigned long within_size_orders =
>>>> READ_ONCE(huge_shmem_orders_within_size);
>>>> unsigned long vm_flags = vma->vm_flags;
>>>> /*
>>>> - * Check all the (large) orders below HPAGE_PMD_ORDER + 1 that
>>>> + * Check all the (large) orders below MAX_PAGECACHE_ORDER +
>>>> 1 that
>>>> * are enabled for this vma.
>>>
>>> Nit:
>>> THP_ORDERS_ALL_FILE_DEFAULT should be self-explanatory enough.
>>> I feel we don't need this comment?
>>
>> Sure.
>>
>> Andrew, please help to squash the following changes into this patch.
>> Thanks.
>
> Maybe drop unsigned long orders too?
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 6af95f595d6f..8485eb6f2ec4 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1638,11 +1638,6 @@ unsigned long shmem_allowable_huge_orders(struct
> inode *inode,
> unsigned long mask = READ_ONCE(huge_shmem_orders_always);
> unsigned long within_size_orders =
> READ_ONCE(huge_shmem_orders_within_size);
> unsigned long vm_flags = vma ? vma->vm_flags : 0;
> - /*
> - * Check all the (large) orders below HPAGE_PMD_ORDER + 1 that
> - * are enabled for this vma.
> - */
> - unsigned long orders = BIT(PMD_ORDER + 1) - 1;
> bool global_huge;
> loff_t i_size;
> int order;
> @@ -1698,7 +1693,7 @@ unsigned long shmem_allowable_huge_orders(struct
> inode *inode,
> if (global_huge)
> mask |= READ_ONCE(huge_shmem_orders_inherit);
>
> - return orders & mask;
> + return THP_ORDERS_ALL_FILE_DEFAULT & mask;
> }
Yes. Good point. Thanks.
(Hope Andrew can help to squash these changes :))
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