From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 338DD18A93F for ; Thu, 4 Jul 2024 09:46:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720086392; cv=none; b=tF41nqOinMGZDVHEcdjUsfAjWRqpoPmhTaG6pxjIEpf4svfQqqJqkcGkcWouGu91/719EhWTc/KcMDyY7Gy5IdK56AfV6Oi2SIJZPoF3lf3bVn/sd/e7dmeFU0RWmyp2vBNgi51l6/ZFapFlfyfK70oXcmw7Wujb3Yl4HUufOmg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720086392; c=relaxed/simple; bh=SFV3U2a3wtGNJ2E+K9zGAxAGhRv5LQCsUDyOoE2gJSo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=X21AMabPkQwNaLNfiuKll4rOLzxsK06QMGxLvmYvnMbPpOnkxT9KsPzEXd/0RSau/FeM1ufKfBEZs3+2C2mpVisIX36x9PZchtxKafdDEU9AbTBdGAtJc5zRizugzHMJPZJcH0GCS1EvjjzDqoORu9mNs10x68cgc3UZRDvHuag= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 BB362367; Thu, 4 Jul 2024 02:46:54 -0700 (PDT) Received: from [10.1.29.168] (XHFQ2J9959.cambridge.arm.com [10.1.29.168]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7AECC3F766; Thu, 4 Jul 2024 02:46:28 -0700 (PDT) Message-ID: Date: Thu, 4 Jul 2024 10:46:27 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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> <8d9e501a-0645-4b78-809a-7c9f49f2106d@arm.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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. 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)