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[2003:cb:c739:2400:78ac:64bb:a39e:2578]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42573c55ff4sm164263945e9.46.2024.07.02.01.28.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 02 Jul 2024 01:28:02 -0700 (PDT) Message-ID: <0c5e16a6-fc23-4602-91d6-81a8742ba221@redhat.com> Date: Tue, 2 Jul 2024 10:28:01 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] support "THPeligible" semantics for mTHP with anonymous shmem To: Ryan Roberts , Yang Shi Cc: Baolin Wang , Bang Li , hughd@google.com, akpm@linux-foundation.org, 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> <06c74db8-4d10-4a41-9a05-776f8dca7189@redhat.com> <429f2873-8532-4cc8-b0e1-1c3de9f224d9@arm.com> <7a0bbe69-1e3d-4263-b206-da007791a5c4@redhat.com> <2450e4f8-236f-49ce-8bd3-b30a6d8c5e57@arm.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: epxwnc5jkwt89k4fxn14yxdhgdrdqjqr X-Rspam-User: X-Rspamd-Queue-Id: 60CFE80003 X-Rspamd-Server: rspam02 X-HE-Tag: 1719908890-508884 X-HE-Meta: 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 Tg+T63oc 7W4U9vR3eOb2KQQPEEE5yEFb+XHSx9ev4fAlQCjClQp5N3nZ3JLZiFd/AYc74BTv765evQqjxGM2LgoePdsLgGt49NPpho1QoGzHBXS2cTxHomqcT/qJvQ6fLFmkbhkJI6qjueCVN1ei20mjuw7xiIGNRzam0OdBJY344h3HIFX2OBA6QnpIGoV+AnAfLg+Zh+5pKdI1maAJAPUpCyfMF29bR1ic8G7FaEsvg+WN4o0z5RUlOoUm3OaOwGdUoyvtBW/3/5/O4OHqBNq61/tKRgJq2gpWugNKmHJv87W5/ei011yF7+zgkAdAnw3FkHenbH6WEnqGoyPCVBtvkbUeoGTPOpWlAKs64DB9Iu6P6uS3s541b7ytGwWAnaqxGbrzdoZgwszMm0jy0w29njzMsP3EsycIWJYaD1uDXwsJt8KynzK2b2bf9NENeew== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 02.07.24 10:24, Ryan Roberts wrote: > On 01/07/2024 19:20, Yang Shi wrote: >> On Mon, Jul 1, 2024 at 3:23 AM David Hildenbrand wrote: >>> >>> On 01.07.24 12:16, Ryan Roberts wrote: >>>> On 01/07/2024 10:17, David Hildenbrand wrote: >>>>> 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] >>>> >>>> Hmm... baby brain? >>> >>> :) >>> >>> I think I only mentioned it in a private mail at some point. >>> >>>> >>>> Sorry about that. I've been a bit useless lately. For some reason it wasn't on >>>> my list, but its there now. Will prioritise it, because I agree it's not good. >>> >>> >>> IIRC, if you do >>> >>> echo never > /sys/kernel/mm/transparent_hugepage/enabled >>> echo always > /sys/kernel/mm/transparent_hugepage/hugepages-2048kB/enabled >>> >>> khugepaged will not get activated. >> >> khugepaged is controlled by the top level knob. > > What do you mean by "top level knob"? I assume > /sys/kernel/mm/transparent_hugepage/enabled ? > > If so, that's not really a thing in its own right; its just the legacy PMD-size > THP control, and we only take any notice of it if a per-size control is set to > "inherit". So if we have: In a simpler world, where "enabled" would have been a boolean (true / false), we could have made it a universal killswitch that is AND'ed with the other ones. Unfortunately, we don't live in such a simple world. -- Cheers, David / dhildenb