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Shutemov" , John Hubbard , David Rientjes , Vlastimil Babka , Hugh Dickins , Kefeng Wang , Barry Song <21cnbao@gmail.com>, Alistair Popple Cc: linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20231204102027.57185-1-ryan.roberts@arm.com> <20231204102027.57185-4-ryan.roberts@arm.com> <004ed23d-5571-4474-b7fe-7bc08817c165@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 2B54A18001A X-Rspam-User: X-Stat-Signature: xnw1ezio5ojm5syehpmbi9k5znj31toe X-Rspamd-Server: rspam01 X-HE-Tag: 1701947592-651533 X-HE-Meta: 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 QH5OO/EN 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 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: >> >>> + >>>       if (!vma->vm_mm)        /* vdso */ >>> -        return false; >>> +        return 0; >>>         /* >>>        * Explicitly disabled through madvise or prctl, or some >>> @@ -88,16 +141,16 @@ bool hugepage_vma_check(struct vm_area_struct *vma, >>> unsigned long vm_flags, >>>        * */ >>>       if ((vm_flags & VM_NOHUGEPAGE) || >>>           test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)) >>> -        return false; >>> +        return 0; >>>       /* >>>        * If the hardware/firmware marked hugepage support disabled. >>>        */ >>>       if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_UNSUPPORTED)) >>> -        return false; >>> +        return 0; >>>         /* khugepaged doesn't collapse DAX vma, but page fault is fine. */ >>>       if (vma_is_dax(vma)) >>> -        return in_pf; >>> +        return in_pf ? orders : 0; >>>         /* >>>        * khugepaged special VMA and hugetlb VMA. >>> @@ -105,17 +158,29 @@ bool hugepage_vma_check(struct vm_area_struct *vma, >>> unsigned long vm_flags, >>>        * VM_MIXEDMAP set. >>>        */ >>>       if (!in_pf && !smaps && (vm_flags & VM_NO_KHUGEPAGED)) >>> -        return false; >>> +        return 0; >>>         /* >>> -     * Check alignment for file vma and size for both file and anon vma. >>> +     * Check alignment for file vma and size for both file and anon vma by >>> +     * filtering out the unsuitable orders. >>>        * >>>        * Skip the check for page fault. Huge fault does the check in fault >>> -     * handlers. And this check is not suitable for huge PUD fault. >>> +     * handlers. >>>        */ >>> -    if (!in_pf && >>> -        !transhuge_vma_suitable(vma, (vma->vm_end - HPAGE_PMD_SIZE))) >>> -        return false; >>> +    if (!in_pf) { >>> +        int order = first_order(orders); >>> +        unsigned long addr; >>> + >>> +        while (orders) { >>> +            addr = vma->vm_end - (PAGE_SIZE << order); >>> +            if (thp_vma_suitable_orders(vma, addr, BIT(order))) >>> +                break; >> >> Comment: you'd want a "thp_vma_suitable_order" helper here. But maybe the >> compiler is smart enough to optimize the loop and everyything else out. > > I'm happy to refactor so that thp_vma_suitable_order() is the basic primitive, > then make thp_vma_suitable_orders() a loop that calls thp_vma_suitable_order() > (that's basically how it is laid out already, just all in one function). Is that > what you are requesting? You got the spirit, yes. >> >> [...] >> >>> + >>> +static ssize_t thpsize_enabled_store(struct kobject *kobj, >>> +                     struct kobj_attribute *attr, >>> +                     const char *buf, size_t count) >>> +{ >>> +    int order = to_thpsize(kobj)->order; >>> +    ssize_t ret = count; >>> + >>> +    if (sysfs_streq(buf, "always")) { >>> +        set_bit(order, &huge_anon_orders_always); >>> +        clear_bit(order, &huge_anon_orders_inherit); >>> +        clear_bit(order, &huge_anon_orders_madvise); >>> +    } else if (sysfs_streq(buf, "inherit")) { >>> +        set_bit(order, &huge_anon_orders_inherit); >>> +        clear_bit(order, &huge_anon_orders_always); >>> +        clear_bit(order, &huge_anon_orders_madvise); >>> +    } else if (sysfs_streq(buf, "madvise")) { >>> +        set_bit(order, &huge_anon_orders_madvise); >>> +        clear_bit(order, &huge_anon_orders_always); >>> +        clear_bit(order, &huge_anon_orders_inherit); >>> +    } else if (sysfs_streq(buf, "never")) { >>> +        clear_bit(order, &huge_anon_orders_always); >>> +        clear_bit(order, &huge_anon_orders_inherit); >>> +        clear_bit(order, &huge_anon_orders_madvise); >> >> Note: I was wondering for a second if some concurrent cames could lead to an >> inconsistent state. I think in the worst case we'll simply end up with "never" >> on races. > > You mean if different threads try to write different values to this file > concurrently? Or if there is a concurrent fault that tries to read the flags > while they are being modified? I thought about what you said first, but what you said last might also apply. As long as "nothing breaks", all good. > > I thought about this for a long time too and wasn't sure what was best. The > existing global enabled store impl clears the bits first then sets the bit. With > this approach you can end up with multiple bits set if there is a race to set > diffierent values, and you can end up with a faulting thread seeing never if it > reads the bits after they have been cleared but before setting them. Right, but user space is playing stupid games and can win stupid prices. As long as nothing breaks, we're good. > > I decided to set the new bit before clearing the old bits, which is different; A > racing fault will never see "never" but as you say, a race to set the file could > result in "never" being set. > > On reflection, it's probably best to set the bit *last* like the global control > does? Probably might just slap a simple spinlock in there, so at least the writer side is completely serialized. Then you can just set the bit last. It's unlikely that readers will actually run into issues, and if they ever would, we could use some rcu magic to let them read a consistent state. -- Cheers, David / dhildenb