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Mon, 01 Jul 2024 01:57:51 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFhuskY2jpqnXAMiCH+ztFwptLwTTk7Ub/sKIkIXMzgIsSHgGTWpW86QHPOoNRn1WZDcaP5lA== X-Received: by 2002:a05:6402:3512:b0:57d:1d79:45b7 with SMTP id 4fb4d7f45d1cf-587a053d9f3mr3139644a12.29.1719824252454; Mon, 01 Jul 2024 01:57:32 -0700 (PDT) Received: from [100.81.188.195] ([178.24.249.76]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5861324f069sm4236982a12.33.2024.07.01.01.57.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 01 Jul 2024 01:57:32 -0700 (PDT) Message-ID: <992cdbf9-80df-4a91-aea6-f16789c5afd7@redhat.com> Date: Mon, 1 Jul 2024 10:57:30 +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> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 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 :) -- Cheers, David / dhildenb