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Date: Mon, 01 Jul 2024 22:51:20 +0800
From: "Bang Li" <libang.li@...group.com>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>,
Ryan Roberts <ryan.roberts@....com>, hughd@...gle.com,
akpm@...ux-foundation.org
Cc: david@...hat.com, wangkefeng.wang@...wei.com, ziy@...dia.com,
linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] support "THPeligible" semantics for mTHP with anonymous
shmem
On 2024/7/1 19:12, Baolin Wang wrote:
>
>
> On 2024/7/1 17:43, Bang Li wrote:
>> Hi, Baolin
>>
>> On 2024/7/1 16:33, Baolin Wang wrote:
>>>
>>>
>>> On 2024/7/1 15:55, Ryan Roberts wrote:
>>>> On 28/06/2024 11:49, Bang Li wrote:
>>>>> After the commit 7fb1b252afb5 ("mm: shmem: add mTHP support for
>>>>> anonymous shmem"), we can configure different policies through
>>>>> the multi-size THP sysfs interface for anonymous shmem. But
>>>>> currently "THPeligible" indicates only whether the mapping is
>>>>> eligible for allocating THP-pages as well as the THP is PMD
>>>>> mappable or not for anonymous shmem, we need to support semantics
>>>>> for mTHP with anonymous shmem similar to those for mTHP with
>>>>> anonymous memory.
>>>>>
>>>>> Signed-off-by: Bang Li <libang.li@...group.com>
>>>>> ---
>>>>> fs/proc/task_mmu.c | 10 +++++++---
>>>>> include/linux/huge_mm.h | 11 +++++++++++
>>>>> mm/shmem.c | 9 +--------
>>>>> 3 files changed, 19 insertions(+), 11 deletions(-)
>>>>>
>>>>> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
>>>>> index 93fb2c61b154..09b5db356886 100644
>>>>> --- a/fs/proc/task_mmu.c
>>>>> +++ b/fs/proc/task_mmu.c
>>>>> @@ -870,6 +870,7 @@ static int show_smap(struct seq_file *m, void *v)
>>>>> {
>>>>> struct vm_area_struct *vma = v;
>>>>> struct mem_size_stats mss = {};
>>>>> + bool thp_eligible;
>>>>> smap_gather_stats(vma, &mss, 0);
>>>>> @@ -882,9 +883,12 @@ static int show_smap(struct seq_file *m, void *v)
>>>>> __show_smap(m, &mss, false);
>>>>> - seq_printf(m, "THPeligible: %8u\n",
>>>>> - !!thp_vma_allowable_orders(vma, vma->vm_flags,
>>>>> - TVA_SMAPS | TVA_ENFORCE_SYSFS, THP_ORDERS_ALL));
>>>>> + thp_eligible = !!thp_vma_allowable_orders(vma, vma->vm_flags,
>>>>> + TVA_SMAPS | TVA_ENFORCE_SYSFS,
>>>>> THP_ORDERS_ALL);
>>>>> + if (vma_is_anon_shmem(vma))
>>>>> + thp_eligible =
>>>>> !!shmem_allowable_huge_orders(file_inode(vma->vm_file),
>>>>> + vma, vma->vm_pgoff, thp_eligible);
>>>>
>>>> Afraid I haven't been following the shmem mTHP support work as much
>>>> as I would
>>>> have liked, but is there a reason why we need a separate function
>>>> for shmem?
>>>
>>> Since shmem_allowable_huge_orders() only uses shmem specific logic to
>>> determine if huge orders are allowable, there is no need to
>>> complicate the thp_vma_allowable_orders() function by adding more
>>> shmem related logic, making it more bloated. In my view, providing a
>>> dedicated helper shmem_allowable_huge_orders(), specifically for
>>> shmem, simplifies the logic.
>>>
>>> IIUC, I agree with David's suggestion that the
>>> shmem_allowable_huge_orders() helper function could be used in
>>> thp_vma_allowable_orders() to support shmem mTHP. Something like:
>>>
>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>>> index c7ce28f6b7f3..9677fe6cf478 100644
>>> --- a/mm/huge_memory.c
>>> +++ b/mm/huge_memory.c
>>> @@ -151,10 +151,13 @@ unsigned long __thp_vma_allowable_orders(struct
>>> vm_area_struct *vma,
>>> * Must be done before hugepage flags check since shmem has its
>>> * own flags.
>>> */
>>> - if (!in_pf && shmem_file(vma->vm_file))
>>> - return shmem_is_huge(file_inode(vma->vm_file),
>>> vma->vm_pgoff,
>>> - !enforce_sysfs, vma->vm_mm,
>>> vm_flags)
>>> - ? orders : 0;
>>> + if (!in_pf && shmem_file(vma->vm_file)) {
>>> + bool global_huge =
>>> shmem_is_huge(file_inode(vma->vm_file), vma->vm_pgoff,
>>> + !enforce_sysfs, vma->vm_mm,
>>> vm_flags);
>>> +
>>> + return
>>> shmem_allowable_huge_orders(file_inode(vma->vm_file),
>>> + vma, vma->vm_pgoff,
>>> global_huge);
>>> + }
>>>
>>> if (!vma_is_anonymous(vma)) {
>>> /*
>>>
>>>> Couldn't (shouldn't) thp_vma_allowable_orders() be taught to handle
>>>> shmem too?
>>>>
>>>>> + seq_printf(m, "THPeligible: %8u\n", thp_eligible);
>>>>> if (arch_pkeys_enabled())
>>>>> seq_printf(m, "ProtectionKey: %8u\n", vma_pkey(vma));
>>>>> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
>>>>> index 212cca384d7e..f87136f38aa1 100644
>>>>> --- a/include/linux/huge_mm.h
>>>>> +++ b/include/linux/huge_mm.h
>>>>> @@ -267,6 +267,10 @@ unsigned long thp_vma_allowable_orders(struct
>>>>> vm_area_struct *vma,
>>>>> return __thp_vma_allowable_orders(vma, vm_flags, tva_flags,
>>>>> orders);
>>>>> }
>>>>> +unsigned long shmem_allowable_huge_orders(struct inode *inode,
>>>>> + struct vm_area_struct *vma, pgoff_t index,
>>>>> + bool global_huge);
>>>>> +
>>>>> struct thpsize {
>>>>> struct kobject kobj;
>>>>> struct list_head node;
>>>>> @@ -460,6 +464,13 @@ static inline unsigned long
>>>>> thp_vma_allowable_orders(struct vm_area_struct *vma,
>>>>> return 0;
>>>>> }
>>>>> +static inline unsigned long shmem_allowable_huge_orders(struct
>>>>> inode *inode,
>>>>> + struct vm_area_struct *vma, pgoff_t index,
>>>>> + bool global_huge)
>>>>> +{
>>>>> + return 0;
>>>>> +}
>>>>> +
>>>>> #define transparent_hugepage_flags 0UL
>>>>> #define thp_get_unmapped_area NULL
>>>>> diff --git a/mm/shmem.c b/mm/shmem.c
>>>>> index d495c0701a83..aa85df9c662a 100644
>>>>> --- a/mm/shmem.c
>>>>> +++ b/mm/shmem.c
>>>>> @@ -1622,7 +1622,7 @@ static gfp_t limit_gfp_mask(gfp_t huge_gfp,
>>>>> gfp_t limit_gfp)
>>>>> }
>>>>> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>>>>> -static unsigned long shmem_allowable_huge_orders(struct inode *inode,
>>>>> +unsigned long shmem_allowable_huge_orders(struct inode *inode,
>>>>> struct vm_area_struct *vma, pgoff_t index,
>>>>> bool global_huge)
>>>>> {
>>>>> @@ -1707,13 +1707,6 @@ static unsigned long
>>>>> shmem_suitable_orders(struct inode *inode, struct vm_fault
>>>>> return orders;
>>>>> }
>>>>> #else
>>>>> -static unsigned long shmem_allowable_huge_orders(struct inode *inode,
>>>>> - struct vm_area_struct *vma, pgoff_t index,
>>>>> - bool global_huge)
>>>>> -{
>>>>> - return 0;
>>>>> -}
>>>>> -
>>>>> static unsigned long shmem_suitable_orders(struct inode *inode,
>>>>> struct vm_fault *vmf,
>>>>> struct address_space *mapping, pgoff_t index,
>>>>> unsigned long orders)
>>
>> Thanks for the reference code. Currently, we only implement the mTHP of
>> anonymous shmem, so we only need to handle anonymous shmem specially. As
>> shown in the following code:
>>
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -151,10 +151,14 @@ unsigned long __thp_vma_allowable_orders(struct
>> vm_area_struct *vma,
>> * Must be done before hugepage flags check since shmem has its
>> * own flags.
>> */
>> - if (!in_pf && shmem_file(vma->vm_file))
>> - return shmem_is_huge(file_inode(vma->vm_file),
>> vma->vm_pgoff,
>> - !enforce_sysfs, vma->vm_mm,
>> vm_flags)
>> - ? orders : 0;
>> + if (!in_pf && shmem_file(vma->vm_file)) {
>> + bool global_huge =
>> shmem_is_huge(file_inode(vma->vm_file), vma->vm_pgoff,
>> + !enforce_sysfs, vma->vm_mm,
>> vm_flags);
>
> Nit: add a blank line after the declaration. Otherwise looks good to me.
It doesn't matter to me whether I add spaces or not, thanks for your
suggestion anyway.
Thanks,
Bang
>
>> + if (!vma_is_anon_shmem(vma))
>> + return global_huge? orders : 0;
>> + return
>> shmem_allowable_huge_orders(file_inode(vma->vm_file),
>> + vma, vma->vm_pgoff,
>> global_huge);
>> + }
>>
>> if (!vma_is_anonymous(vma)) {
>>
>> Thanks,
>> Bang
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