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Mon, 01 Jul 2024 02:17:05 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFQO+mw0HIQrpIoRiR06Vb4TqsJHQt+K4E4AVASOFBZIuBjkVxCtUF7sORg7CS7dEolwe0UHg== X-Received: by 2002:a17:906:7c96:b0:a6f:52db:7e5e with SMTP id a640c23a62f3a-a7514428746mr323652966b.19.1719825424556; Mon, 01 Jul 2024 02:17:04 -0700 (PDT) Received: from [100.81.188.195] ([178.24.249.76]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a72b2739395sm278778966b.157.2024.07.01.02.17.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 01 Jul 2024 02:17:04 -0700 (PDT) Message-ID: <06c74db8-4d10-4a41-9a05-776f8dca7189@redhat.com> Date: Mon, 1 Jul 2024 11:17:03 +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> <597ac51e-3f27-4606-8647-395bb4e60df4@redhat.com> <6f68fb9d-3039-4e38-bc08-44948a1dae4d@arm.com> <992cdbf9-80df-4a91-aea6-f16789c5afd7@redhat.com> <2e0a1554-d24f-4d0d-860b-0c2cf05eb8da@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 11:14, Ryan Roberts wrote: > On 01/07/2024 09:57, David Hildenbrand wrote: >> On 01.07.24 10:50, Ryan Roberts wrote: >>> On 01/07/2024 09:48, David Hildenbrand wrote: >>>> 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. >>> >>> Are you planning to do that, or do you want me to send a patch? >> >> I'm planning on looking into some details, especially the interaction with large >> folios in the pagecache. I'll let you know once I have a better idea what >> actually should be done :) > > OK great - I'll scrub it from my todo list... really getting things done today :) Resolved the khugepaged thiny already? :P [khugepaged not active when only enabling the sub-size via the 2M folder IIRC] -- Cheers, David / dhildenb