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 843E84D59F for ; Wed, 3 Jul 2024 10:25:31 +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=1720002333; cv=none; b=GfxpPnplxBhrO2vfzDgg6MGaXDp+DzggMOfOzzDZDe1TonC07nVbGVPziXmUxDGCjEtgxVD3AnpL0PhgSCMhVB6i4laeMMJPGusoUSWIBur8XL/DlX58z8OsMWrSicrRvl+wOwr1MTvmFKje8eN1YVI4TCgGucX9w8MZ/yeNO60= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720002333; c=relaxed/simple; bh=3f/Mhc2hIGGeD97HQqVWSaejltHUsjGGJDXrJkw43lk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=md4Hwr7ycSH9CyFOIB1XZ0e4ygRZ5+cUOxjvs4TefMsugIco3ibLrHOwT40b0jwFznpw+3khWLb32BXOalhV8kNPS7pR/F8pZMFV0AU4IEKGaLpNn1fpVcSOLdTUUbu1Qjj2xyVPMcNBxVGRsTep0PvuuEVsp5fsmcDNbTtnuAk= 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 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 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> From: Ryan Roberts In-Reply-To: <8c018e06-74f1-46e9-bc32-b3870342cdc1@antgroup.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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)