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imf27.hostedemail.com; dkim=none; spf=pass (imf27.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1720002321; a=rsa-sha256; cv=none; b=0WeEFyA9R7E+RgN7Z98nO2w7mtfUJFclB95k75g9IOwbrucUgcOsQGmJHg+XXPYUH4sILG 7KZwzrrbcwllAHb2sz5OFdIIyCBbNVAuuX2okHMNbqLiWu4pEJJIYQkAsmD5yVO6H9XVU/ DdVIp7+pv4B6eiEHA9UyvaLfY+AP7PU= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E114B367; Wed, 3 Jul 2024 03:25:55 -0700 (PDT) Received: from [10.57.74.76] (unknown [10.57.74.76]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 629003F766; Wed, 3 Jul 2024 03:25:29 -0700 (PDT) Message-ID: <8d9e501a-0645-4b78-809a-7c9f49f2106d@arm.com> Date: Wed, 3 Jul 2024 11:25:27 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: thp: support "THPeligible" semantics for mTHP with anonymous shmem Content-Language: en-GB To: Bang Li , ughd@google.com, akpm@linux-foundation.org Cc: david@redhat.com, wangkefeng.wang@huawei.com, baolin.wang@linux.alibaba.com, ioworker0@gmail.com, ziy@nvidia.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20240702023401.41553-1-libang.li@antgroup.com> <507da6d0-77c5-46ca-8351-53b405ecb131@arm.com> <8c018e06-74f1-46e9-bc32-b3870342cdc1@antgroup.com> From: Ryan Roberts In-Reply-To: <8c018e06-74f1-46e9-bc32-b3870342cdc1@antgroup.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 08A9C40017 X-Stat-Signature: dgagy1eegek5kz7darb5xkgo778icrte X-HE-Tag: 1720002331-934268 X-HE-Meta: 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 fW/ekhbx OUhZ8OzyvshhGuhTi8Ostn3sDaU5mpBOiNMX/HRHESeOI8rWy/G6AY58OuMAlBaoldTyu9FQYpIVRPq91bwBROL0wyquuZmfQc0ZZpTmqWvIHSgNcoro4R/WXSgHjtvyyQvNLmXQYro1AAMdTaeINedwe2oSOURiLU+LN+IIGt+offfi5SmlXtAPOZUH2GuIXPaaZNnVLW8f/zZY9L2gkc8p6ZD3bj6+dJrAjPOkkAwVxwbQ4Qt/lmHLCUTviaUSyrjQxPUF7Ltjn20fn0rjlw1kvoTyUYD9uM7sA X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 03/07/2024 08:33, Bang Li wrote: > Hi Ryan, > > Thanks for the review! > > On 2024/7/2 16:18, Ryan Roberts wrote: >> On 02/07/2024 03:34, 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 >>> --- >>> Changes since v1 [1]: >>>   - Put anonymous shmem mthp related logic into >>>     thp_vma_allowable_orders() (per David) >>> >>> [1] >>> https://lore.kernel.org/linux-mm/20240628104926.34209-1-libang.li@antgroup.com/ >>> --- >>>   include/linux/huge_mm.h | 11 +++++++++++ >>>   mm/huge_memory.c        | 13 +++++++++---- >>>   mm/shmem.c              |  9 +-------- >>>   3 files changed, 21 insertions(+), 12 deletions(-) >>> >>> 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/huge_memory.c b/mm/huge_memory.c >>> index c7ce28f6b7f3..ea377bb4af91 100644 >>> --- a/mm/huge_memory.c >>> +++ b/mm/huge_memory.c >>> @@ -151,10 +151,15 @@ 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); >>> + >>> +        if (!vma_is_anon_shmem(vma)) >>> +            return global_huge? orders : 0; >> >> nit: missing space before '?' > > Yes, thanks. > >> >>> +        return shmem_allowable_huge_orders(file_inode(vma->vm_file), >>> +                            vma, vma->vm_pgoff, global_huge); >> >> What's the rationale for splitting these functions into shmem_is_huge() and >> shmem_allowable_huge_orders()? Why not just have a single >> shmem_allowable_huge_orders() that tells you the answer? >> > > Currently, shmem_is_huge() is used for all shmem implementations to determine > whether the conditions for using THP are met. And shmem_allowable_huge_orders() > is currently mainly used for anonymous shmem's mTHP to obtain all orders that > meet the conditions. In my opinion, there is no problem in separating these two > functions. In the future, when mTHP of other shmem types is also implemented, > will shmem_is_huge() be unnecessary? Personally, I consider shmem_is_huge() to be superfluous; If you have one function, shmem_allowable_huge_orders(), that gives you all the information you need. If the inode only allows PMD-size, then only return that bit in the field. IMHO removing shmem_is_huge() would make things more readable. Thanks, Ryan > > Thanks, > Bang > >>> +    } >>>         if (!vma_is_anonymous(vma)) { >>>           /* >>> 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)