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Received: from 30.230.83.123(mailfrom:libang.li@antgroup.com fp:SMTPD_---.YHL2Og._1720087543) by smtp.aliyun-inc.com; Thu, 04 Jul 2024 18:05:43 +0800 Message-ID: <941458a6-9e74-444a-9dfd-726d0a7cf158@antgroup.com> Date: Thu, 04 Jul 2024 18:05:42 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: thp: support "THPeligible" semantics for mTHP with anonymous shmem To: Ryan Roberts , 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> <8d9e501a-0645-4b78-809a-7c9f49f2106d@arm.com> Content-Language: en-US From: "Bang Li" In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: iu75k1xs7h8oqtuaadimdzom5fe3ifag X-Rspam-User: X-Rspamd-Queue-Id: 2F06740023 X-Rspamd-Server: rspam02 X-HE-Tag: 1720087547-101941 X-HE-Meta: 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 Lkq/1lfl E6Yd1rLbFR7NY+TUbbxmXyEF6ImJ1Ieze5L/0TtCGuE/mKT6QEbC2/2npInjL9RsKt9kpmvSZ/5T7SRTFnoWSa61iemRw539SIybCoN5eZ4mhI7xjC80/1A0QRSHiVCBCeYjvP+SgJnu3hDQYc1QNWsPNhtZLNpGAW8lYXTgfiOjutkfBu+1MT6vD76/LRgoeY5f0kiqPcRdOWXYVhNhMErArn+3atzSub8OK9AvRxCdlF4t3acec5l9WptjbRQec/liWLUsH7ZBpNGnjKvP3nMliuXvz5pREW/Q12Vs8ONIDMjO3m01L1zn5yiPNX13CKSf20w/ulkJegplnSspa2o/TBvBlPaf9odIdTojUpJJwOi5k6cN4Jz+AnRUUJnwV6U06Cd3ATTQmu152NYcaHRHVJAkbmAcWRshG 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: Hi Ryan, On 2024/7/4 17:46, Ryan Roberts wrote: > On 03/07/2024 17:02, Bang Li wrote: >> On 2024/7/3 18:25, Ryan Roberts wrote: >>> 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. >> >> Thank you very much for your opinion. I think there is no big problem in keeping >> the current interface status quo. In my opinion, when we implement mTHP for all >> shmems, it may be better to remove shmem_is_huge() and use >> shmem_allowable_huge_orders() uniformly. I believe that it won't be long before >> someone proposes a non-anonymous shared mTHP patchset. Anyway, thank you for >> your suggestion :). > > See [1] for an expanded list of concerns I have about the current state of the > interface and implementation. OK, could you please send me the corresponding link ;)？ Thanks， Bang > > Thanks, > Ryan > >> >> Thanks, >> Bang >> >>> >>> 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)