From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 684282F37 for ; Thu, 4 Jul 2024 14:02:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720101722; cv=none; b=YjY5HhgAxsGf3gYEaGrWNLDJltcHgnGV0T/Yroprc99ATXfXztg57OUUWsP8FXx3+k2jNCTiAThRgHI5XL2ysjrEo8sXzXUJrjxSIUIJthmo8m91RALMqVsgBCXP+/amjOM1IDCHvO2K63uBBS8epaCNjpG6u/GWn4iYrpU08B4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720101722; c=relaxed/simple; bh=tXs40RkUPU9MgEkVuQ/+eDd2bXv7Kl4yuojJamwKrkM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=oUD9fpa/ClrjR7nNt5ePxJ+A1fGFVDl4l7m3Hkt7LZbiWL8bQudRBq6TE1JEgyq3ck9fsCCJXIxZ8UJv/D2MA3DxnGgcMqzRGuGabSsHAS0wD5kIg0TZT0pe2n00SUpDtSNaQ7szaEcCdTNDnhfxiZBa8XdpLeokAK21/5FUrq8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=GiO12IlS; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="GiO12IlS" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1720101719; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=88tDGw0lvfCvEqqU6cpCNtQ9t7rNAK6rugjju/WdUSc=; b=GiO12IlSDvKEV366LT16IMmw2gXsmwj3AjrOyp2mpxclFEl746xSKQE7MTJayr2OJcSOIi SAx0DQ7GaFUCfUUB0iy85oxY9xFvd8I4V2yEcpsmUvs8O09qNL9ZRtCIt5uZlIJojOFi/4 7rEWP2wcGTH/oQhaQLeXc9Pp1kEbFy0= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-288-nnCtgcnSO1KY2RhNPoJdcA-1; Thu, 04 Jul 2024 10:01:58 -0400 X-MC-Unique: nnCtgcnSO1KY2RhNPoJdcA-1 Received: by mail-wm1-f70.google.com with SMTP id 5b1f17b1804b1-4256809ae27so4531325e9.1 for ; Thu, 04 Jul 2024 07:01:57 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1720101717; x=1720706517; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=88tDGw0lvfCvEqqU6cpCNtQ9t7rNAK6rugjju/WdUSc=; b=wIVy6ohLB7inbdmK6/EoRlmL2FZPxsRHVxgAPxe+q/KhlpbJY8dgwmNsYNAPabWNmE MZsXBdlYUa05WsPk+Y+80lJyQc81fq52THuanIkrVVdtxXMSuHULZd59lrUQOvdan5uu qBusv7/mQaCq1QDhZsChS6b865oigPUof3Ohv2uya/uHXA80lZ23O9og0+xF6BaqOtBF +xrk4twdsA6AK2Sy7xx4pSLJgPQFACUaqz/8IXM99F90mNukz2LkejfdY4dkybdWhfTz jkbs0YfZSsxZbCTR4GD0/hk3lpDENpda02KdIVUMrY80vli60IEqjNPVV37Jc+ok62nJ iDnA== X-Forwarded-Encrypted: i=1; AJvYcCX5mrz67/6KY/lsLwIgFFyR/M8D/GtTovViKWYYZg50HDAtYflyKHYvTJWzO7am2WaTR+l1yOhWqEDuPp4Ugi+JEDgvWmJFq9qFe29M X-Gm-Message-State: AOJu0YzeoVQnRoAE0y/UgSQng8ETtJop+uXh7EQHqCP8t5ZxRIhz9DWg zpWpBg18ygZ9hkwQQ6hSJEZYrCySpCJ7LBwhh6ImNksLbLVHv3KwKuvm/5/oQKWOApNGWc46iZ2 AKYAD4s6leQU9tafkt8chN+B3pPsp09I8aphkB1s7L057kFfTymYkmBuUt/FEsw== X-Received: by 2002:a05:600c:6dd9:b0:425:78a9:b3cc with SMTP id 5b1f17b1804b1-4264a3e76c8mr14444215e9.17.1720101716905; Thu, 04 Jul 2024 07:01:56 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEt7+R5Ll1HHYZlKdhlvsRJnkI27w9SfajWwIq0NEZ/kcpKH3Li8qi5hSS5cLEpOjwFHf5sBg== X-Received: by 2002:a05:600c:6dd9:b0:425:78a9:b3cc with SMTP id 5b1f17b1804b1-4264a3e76c8mr14443915e9.17.1720101716389; Thu, 04 Jul 2024 07:01:56 -0700 (PDT) Received: from ?IPV6:2003:cb:c715:8600:f05d:97b6:fb98:2bc1? (p200300cbc7158600f05d97b6fb982bc1.dip0.t-ipconnect.de. [2003:cb:c715:8600:f05d:97b6:fb98:2bc1]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4264a1d510bsm26214875e9.3.2024.07.04.07.01.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 04 Jul 2024 07:01:55 -0700 (PDT) Message-ID: Date: Thu, 4 Jul 2024 16:01:54 +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 v5 4/6] mm: shmem: add mTHP support for anonymous shmem To: Ryan Roberts , Baolin Wang , akpm@linux-foundation.org, hughd@google.com Cc: willy@infradead.org, wangkefeng.wang@huawei.com, ying.huang@intel.com, 21cnbao@gmail.com, shy828301@gmail.com, ziy@nvidia.com, ioworker0@gmail.com, da.gomez@samsung.com, p.raghav@samsung.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <65796c1e72e51e15f3410195b5c2d5b6c160d411.1718090413.git.baolin.wang@linux.alibaba.com> <65c37315-2741-481f-b433-cec35ef1af35@arm.com> <475332ea-a80b-421c-855e-a663d1d5bfc7@linux.alibaba.com> From: David Hildenbrand Content-Language: en-US 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: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 04.07.24 15:58, Ryan Roberts wrote: > On 04/07/2024 12:15, Baolin Wang wrote: >> >> >> On 2024/7/4 01:25, Ryan Roberts wrote: >>> On 11/06/2024 11:11, Baolin Wang wrote: >>>> Commit 19eaf44954df adds multi-size THP (mTHP) for anonymous pages, that >>>> can allow THP to be configured through the sysfs interface located at >>>> '/sys/kernel/mm/transparent_hugepage/hugepage-XXkb/enabled'. >>>> >>>> However, the anonymous shmem will ignore the anonymous mTHP rule >>>> configured through the sysfs interface, and can only use the PMD-mapped >>>> THP, that is not reasonable. Users expect to apply the mTHP rule for >>>> all anonymous pages, including the anonymous shmem, in order to enjoy >>>> the benefits of mTHP. For example, lower latency than PMD-mapped THP, >>>> smaller memory bloat than PMD-mapped THP, contiguous PTEs on ARM architecture >>>> to reduce TLB miss etc. In addition, the mTHP interfaces can be extended >>>> to support all shmem/tmpfs scenarios in the future, especially for the >>>> shmem mmap() case. >>>> >>>> The primary strategy is similar to supporting anonymous mTHP. Introduce >>>> a new interface '/mm/transparent_hugepage/hugepage-XXkb/shmem_enabled', >>>> which can have almost the same values as the top-level >>>> '/sys/kernel/mm/transparent_hugepage/shmem_enabled', with adding a new >>>> additional "inherit" option and dropping the testing options 'force' and >>>> 'deny'. By default all sizes will be set to "never" except PMD size, >>>> which is set to "inherit". This ensures backward compatibility with the >>>> anonymous shmem enabled of the top level, meanwhile also allows independent >>>> control of anonymous shmem enabled for each mTHP. >>>> >>>> Signed-off-by: Baolin Wang >>> >>> [...] >>> >>> Hi Baolin, >>> >>> I'm currently trying to fix a bug where khugepaged is not started if only shmem >>> is enabled for THP. See discussion at [1]. It's been broken like this forever. >>> >>> Assuming anon and shmem THP are initially both disabled: >>> >>> # echo never > /sys/kernel/mm/transparent_hugepage/shmem_enabled >>> # echo never > /sys/kernel/mm/transparent_hugepage/enabled >>> >>> >>> Then shemem THP is enabled: >>> >>> # echo always > /sys/kernel/mm/transparent_hugepage/shmem_enabled >>> >> >> Thanks Ryan. Yes, this is a real problem. >> >>> As part of investigating the fix, I stumbled upon this patch, which I remember >>> reviewing an early version of but I've been out for a while and missed the >>> latter versions. See below for comments and questions; the answers to which will >>> help me figure out how to fix the above... >>> >>> [1] >>> https://lore.kernel.org/linux-mm/20240702144617.2291480-1-ryan.roberts@arm.com/ >>> >>> >>>>   +#ifdef CONFIG_TRANSPARENT_HUGEPAGE >>>> +static unsigned long shmem_allowable_huge_orders(struct inode *inode, >>>> +                struct vm_area_struct *vma, pgoff_t index, >>>> +                bool global_huge) >>>> +{ >>>> +    unsigned long mask = READ_ONCE(huge_shmem_orders_always); >>>> +    unsigned long within_size_orders = >>>> READ_ONCE(huge_shmem_orders_within_size); >>>> +    unsigned long vm_flags = vma->vm_flags; >>>> +    /* >>>> +     * Check all the (large) orders below HPAGE_PMD_ORDER + 1 that >>>> +     * are enabled for this vma. >>>> +     */ >>>> +    unsigned long orders = BIT(PMD_ORDER + 1) - 1; >>>> +    loff_t i_size; >>>> +    int order; >>>> + >>>> +    if ((vm_flags & VM_NOHUGEPAGE) || >>>> +        test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)) >>>> +        return 0; >>>> + >>>> +    /* If the hardware/firmware marked hugepage support disabled. */ >>>> +    if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_UNSUPPORTED)) >>>> +        return 0; >>>> + >>>> +    /* >>>> +     * Following the 'deny' semantics of the top level, force the huge >>>> +     * option off from all mounts. >>>> +     */ >>>> +    if (shmem_huge == SHMEM_HUGE_DENY) >>>> +        return 0; >>> >>> I don't quite get this, I don't think its the desirable behaviour. This is >>> saying that if the top-level shemem_enabled control is set to 'deny', then all >>> mTHP sizes, regardless of their control's setting are disabled? >>> >>> The anon controls don't work like that; you can set the top-level control to >>> anything you like, but its only consumed if the per-size controls are >>> inheriting it. >> >> IMO, 'deny' option is not similar like 'never' option. >> >>> >>> So for the deny case, wouldn't it be better to allow that as an option on all >>> the per-size controls (and implicitly let it be inherrited from the top-level)? >> >> From 'deny' option's semantics: >> "disables huge on shm_mnt and all mounts, for emergency use;" > > Right. Today, tmpfs only supports PMD-sized THP. So for all per-size controls > except the PMD-size control, 'deny' and 'never' would be the same practically > speaking. For the PMD-size control, 'deny' would disable THP for both anon shmem > and all tmpfs mounts, whereas 'never' would only disable THP for anon shmem. > When tmpfs gains mTHP support, 'deny' in the other per-size controls would also > disable that size for the tmpfs mounts. > > I disagree with the current implementation where setting it up so that a > top-level 'deny' overrides whatever is in the per-size controls simply because > it's different to the model implemented for anon THP. That's my 2 cents. If > nobody else agrees then that ok - I'll fix the above bug according to the > current model. IIRC, Hugh said that deny+force are rather legacy artifacts that we don't want on sub-controls (and likely we cannot remove them). I agree they shouldn't overwrite other toggles. The models we used should better match. -- Cheers, David / dhildenb