From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 E39371B6D1C for ; Tue, 3 Dec 2024 19:07:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733252868; cv=none; b=eJFb6WNaoyl4I9eHC9r4CmqOs/aTd08PFlgmooBTdZVXQZA3diOnJn+WDujH2ghC8Pk17/G8WJLWpnbYUamLdGWoXXAI7h/fiOfPs8zekpiplxgbF9EK0uuS7jcFtYRMcJBQqcYpQyxEnKCYOGGG1Xw6SVr2pWiJDI9N3UGM7e4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733252868; c=relaxed/simple; bh=Z8fBsRLGvyTVhA923Wu3wCfNY2ZltbxLl/UWtH0QTYM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=C474LNJg70BqDMu1+5xmN8qMJ4qMCXHNb/kd2J/hTv3EWEbzrdWRIyTcvcB+1Gg7KH+ZnKZ+DbQB2r1SRl7guCElSQR5zxanyNSZzEuCK01KuT5SHCxEx5bmtVwIeO79YO+24KU59+zSL3C0oazESOrCqWxcLGASLEe0J1/ZafI= 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=Kd0aa6Hv; arc=none smtp.client-ip=170.10.129.124 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="Kd0aa6Hv" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1733252864; 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=qp8qIC8+SbNjtJ/vD3Mc/pgGXMGuySIroHQBH4DmWNM=; b=Kd0aa6HvDYvY0EbeKs/Kn1bj/qP8SXR4sJXzoes3zV1sZV2YWWcNJMzeAZfvhA1RxvYBk5 Z9v/kgiPeRFK5tNFtBnYGeTC828SUKD3nfpOBiHWtzqs5mu8fvXiiZlsoGUrXmYWetxEWw v6xYJL9b4IuO4xoaEfIPXNOQkfRBSYA= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-687-mTHdFrMgMtaJ2CFzRdIXGA-1; Tue, 03 Dec 2024 14:07:41 -0500 X-MC-Unique: mTHdFrMgMtaJ2CFzRdIXGA-1 X-Mimecast-MFC-AGG-ID: mTHdFrMgMtaJ2CFzRdIXGA Received: by mail-wm1-f71.google.com with SMTP id 5b1f17b1804b1-434a27c9044so33838865e9.0 for ; Tue, 03 Dec 2024 11:07:41 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1733252860; x=1733857660; 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=qp8qIC8+SbNjtJ/vD3Mc/pgGXMGuySIroHQBH4DmWNM=; b=LR9Fhr+0cfvytT/zf/0PxaAqLVUDinbjGcvn2EiZVQ1L74z5p/41w6kxPN9rpiTTea kC4gcrnrsDkH1qi+/JCEUvjOmWsmTElVhHPDF2j0Hyb1m9+UdVVOh+z6SI74RgbpLVDT 7nQR6GPN2q06kb1DSVB922Goes/aZ9NwQmpDLloPjb4nN8Ow+JgDYmXLzQ0bdDcOoYF6 W290SI0ACtpmVJtRGYlPQBx5aLSRQK9OYsmjlMMOHCItrCkNeB+n6fyttBcgVtGQIsWD H9UeEGGDWH8eopjCHTVDirqlLMb2ytf5mIWqIkFsmkaK5G1/0C/9vetI51MwtXVIFSZr ADcA== X-Gm-Message-State: AOJu0Yx8USUJIgw84lvF0wn+mTU1xvupxXuGEWy+AZrFxYpLO5rpeYeE SySyzHGRQnEbZhqxOPX+W7ZXtK+q4wmBi0QnyMX+ro8nYDhkqw540y9GNmDW4cuaOTUaReK0PCX kVeilLAWO9YcQTHkkLVblUNUyJGD/1Q1zJ479COj6dWc3wNmIrUArs7G1Xpl1Jw== X-Gm-Gg: ASbGncuXJTRcgrEWyNJu2J6jGClQdMVczbXyOgKY9rUP/O5SWJdyM4A6BwTc50/tPrU Dm0lRN7TqsenX1ryBtGuQyoSgYC7RJdUyOBDOjt1wSEevlmNi+MCCMh2Hseqef1SfukbEDwJRsN vFeyXXI9qnPoSgxaYlpkjDkPGzIEqTLP2A0l5cYOvbtFK8Mo/pz+hBwMtDP4mxCdsK8KkiIELLO Q0sv1qhKToWSqYmXZZHrBgJw3tGsMcEmjzflO7PSgM32N+u+5anQ6RWFF9nlHOxiwTN4kbugmfe ACuU5S9pEcm+ZNMLBW/NtZMNFUFs1HLo74WhMpfcgSAdsN6hJGPAke6VzIZrhfpFCEPuTFdG+oC N4w== X-Received: by 2002:a05:600c:1c1d:b0:434:932b:a44c with SMTP id 5b1f17b1804b1-434d3fe339emr12878675e9.27.1733252860308; Tue, 03 Dec 2024 11:07:40 -0800 (PST) X-Google-Smtp-Source: AGHT+IEzqV5rcPa1XB7yoDaMRtuRh1kpD7s5D32r4FS5ciVaVbd7QdQZuGmrecP2reRzXahF4Ztg4g== X-Received: by 2002:a05:600c:1c1d:b0:434:932b:a44c with SMTP id 5b1f17b1804b1-434d3fe339emr12878455e9.27.1733252859940; Tue, 03 Dec 2024 11:07:39 -0800 (PST) Received: from ?IPV6:2003:cb:c746:1b00:fd9e:c26c:c552:1de7? (p200300cbc7461b00fd9ec26cc5521de7.dip0.t-ipconnect.de. [2003:cb:c746:1b00:fd9e:c26c:c552:1de7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-385e13e8eadsm12068257f8f.28.2024.12.03.11.07.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Dec 2024 11:07:38 -0800 (PST) Message-ID: Date: Tue, 3 Dec 2024 20:07:36 +0100 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 RESEND v2 4/6] mm/page_alloc: sort out the alloc_contig_range() gfp flags mess To: Zi Yan , Vlastimil Babka Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, Andrew Morton , Oscar Salvador , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Naveen N Rao , Madhavan Srinivasan References: <20241203094732.200195-1-david@redhat.com> <20241203094732.200195-5-david@redhat.com> <96c92857-4850-4f85-9474-ac193c5ea48c@redhat.com> <04c1d28e-bbea-4499-9a6d-770f9ca53ba9@suse.cz> <498871B1-D26C-4934-8E89-C6C8ECE8872A@nvidia.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: <498871B1-D26C-4934-8E89-C6C8ECE8872A@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 03.12.24 16:49, Zi Yan wrote: > On 3 Dec 2024, at 9:24, Vlastimil Babka wrote: > >> On 12/3/24 15:12, David Hildenbrand wrote: >>> On 03.12.24 14:55, Vlastimil Babka wrote: >>>> On 12/3/24 10:47, David Hildenbrand wrote: >>>>> It's all a bit complicated for alloc_contig_range(). For example, we don't >>>>> support many flags, so let's start bailing out on unsupported >>>>> ones -- ignoring the placement hints, as we are already given the range >>>>> to allocate. >>>>> >>>>> While we currently set cc.gfp_mask, in __alloc_contig_migrate_range() we >>>>> simply create yet another GFP mask whereby we ignore the reclaim flags >>>>> specify by the caller. That looks very inconsistent. >>>>> >>>>> Let's clean it up, constructing the gfp flags used for >>>>> compaction/migration exactly once. Update the documentation of the >>>>> gfp_mask parameter for alloc_contig_range() and alloc_contig_pages(). >>>>> >>>>> Acked-by: Zi Yan >>>>> Signed-off-by: David Hildenbrand >>>> >>>> Reviewed-by: Vlastimil Babka >>>> >>>>> + /* >>>>> + * Flags to control page compaction/migration/reclaim, to free up our >>>>> + * page range. Migratable pages are movable, __GFP_MOVABLE is implied >>>>> + * for them. >>>>> + * >>>>> + * Traditionally we always had __GFP_HARDWALL|__GFP_RETRY_MAYFAIL set, >>>>> + * keep doing that to not degrade callers. >>>>> + */ >>>> >>>> Wonder if we could revisit that eventually. Why limit migration targets by >>>> cpuset via __GFP_HARDWALL if we were not called with __GFP_HARDWALL? And why >>>> weaken the attempts with __GFP_RETRY_MAYFAIL if we didn't specify it? >>> >>> See below. >>> >>>> >>>> Unless I'm missing something, cc->gfp is only checked for __GFP_FS and >>>> __GFP_NOWARN in few places, so it's mostly migration_target_control the >>>> callers could meaningfully influence. >>> >>> Note the fist change in the file, where we now use the mask instead of coming up >>> with another one out of the blue. :) >> >> I know. What I wanted to say - cc->gfp is on its own only checked in few >> places, but now since we also translate it to migration_target_control's >> gfp_mask, it's mostly that part the caller might influence with the passed >> flags. But we still impose own additions to it, limiting that influence. >> >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>> index ce7589a4ec01..54594cc4f650 100644 >>> --- a/mm/page_alloc.c >>> +++ b/mm/page_alloc.c >>> @@ -6294,7 +6294,7 @@ static int __alloc_contig_migrate_range(struct compact_control *cc, >>> int ret = 0; >>> struct migration_target_control mtc = { >>> .nid = zone_to_nid(cc->zone), >>> - .gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL, >>> + .gfp_mask = cc->gfp_mask, >>> .reason = MR_CONTIG_RANGE, >>> }; >>> >>> GFP_USER contains __GFP_HARDWALL. I am not sure if that matters here, but >> >> Yeah wonder if GFP_USER was used specifically for that part, or just randomly :) >> >>> likely the thing we are assuming here is that we are migrating a page, and >>> usually, these are user allocation (except maybe balloon and some other non-lru >>> movable things). >> >> Yeah and user allocations obey cpuset and mempolicies etc. But these are >> likely somebody elses allocations that were done according to their >> policies. With our migration we might be actually violating those, which >> probably can't be helped (is at least migration within the same node >> preferred? hmm). But it doesn't seem to me that our caller's restrictions >> (if those exist, would be enforced by __GFP_HARDWALL) are that relevant for >> somebody else's pages? > > Yeah, I was wondering why current_gfp_context() is used to adjust gfp_mask, > since current context might not be relevant. But I see it is used in > the original code, so I did not ask. If current context is irrelevant w.r.t > the to-be-migrated pages, should current_gfp_context() part be removed? Please see how current_gfp_context() is only concerned (excluding the __GFP_MOVABLE thing we unconditionally set ...) about reclaim flags. This part make absolute sense to respect here. So that is something different than __GFP_HARDWALL that *we so far unconditionally set* and is not a "reclaim" flag. -- Cheers, David / dhildenb