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Mon, 01 Jul 2024 01:48:23 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFCWELm7mnv/AkmKHD7/2/AQCxBkYAF1WqSVsLcGRLWTkITOLJVeRTnLjIOX8Xx0MIkCiBHlQ== X-Received: by 2002:a05:6402:11c9:b0:57d:785:7cc2 with SMTP id 4fb4d7f45d1cf-587a053e368mr3195748a12.28.1719823702590; Mon, 01 Jul 2024 01:48:22 -0700 (PDT) Received: from [100.81.188.195] ([178.24.249.76]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-58612c83529sm4146372a12.6.2024.07.01.01.48.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 01 Jul 2024 01:48:22 -0700 (PDT) Message-ID: <597ac51e-3f27-4606-8647-395bb4e60df4@redhat.com> Date: Mon, 1 Jul 2024 10:48:21 +0200 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] support "THPeligible" semantics for mTHP with anonymous shmem To: Ryan Roberts , Baolin Wang , Bang Li , hughd@google.com, akpm@linux-foundation.org Cc: wangkefeng.wang@huawei.com, ziy@nvidia.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20240628104926.34209-1-libang.li@antgroup.com> <4b38db15-0716-4ffb-a38b-bd6250eb93da@arm.com> <4d54880e-03f4-460a-94b9-e21b8ad13119@linux.alibaba.com> <516aa6b3-617c-4642-b12b-0c5f5b33d1c9@arm.com> Content-Language: en-US From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 01.07.24 10:40, Ryan Roberts wrote: > On 01/07/2024 09:33, 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 >>>> --- >>>>   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. > > My point was really that a single interface (thp_vma_allowable_orders) should be > used to get this information. I have no strong opinon on how the implementation > of that interface looks. What you suggest below seems perfectly reasonable to me. Right. thp_vma_allowable_orders() might require some care as discussed in other context (cleanly separate dax and shmem handling/orders). But that would be follow-up cleanups. -- Cheers, David / dhildenb