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[2003:cb:c71c:4e00:b097:7075:f6ba:300a]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-36d2715716esm4728486f8f.5.2024.08.09.02.32.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 09 Aug 2024 02:32:02 -0700 (PDT) Message-ID: <75eb6e75-8a6d-460a-8e96-7496ed1396b7@redhat.com> Date: Fri, 9 Aug 2024 11:32:01 +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 v2] mm: Override mTHP "enabled" defaults at kernel cmdline To: Barry Song Cc: Ryan Roberts , Andrew Morton , Jonathan Corbet , Lance Yang , Baolin Wang , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20240808101700.571701-1-ryan.roberts@arm.com> <99b78488-c524-4269-b1fb-a13eaa4f274c@redhat.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 09.08.24 11:24, Barry Song wrote: > On Fri, Aug 9, 2024 at 5:19 PM David Hildenbrand wrote: >> >> On 08.08.24 12:16, Ryan Roberts wrote: >>> Add thp_anon= cmdline parameter to allow specifying the default >>> enablement of each supported anon THP size. The parameter accepts the >>> following format and can be provided multiple times to configure each >>> size: >>> >>> thp_anon=[KMG]: >>> >>> See Documentation/admin-guide/mm/transhuge.rst for more details. >>> >>> Configuring the defaults at boot time is useful to allow early user >>> space to take advantage of mTHP before its been configured through >>> sysfs. >> >> I suspect a khugeapged enhancement and/or kernel-config-dependant >> defaults and/or early system settings will also be able to mitigate that >> without getting kernel cmdlines involved in the future. >> >>> >>> Signed-off-by: Ryan Roberts >>> --- >>> >>> Hi All, >>> >>> I've split this off from my RFC at [1] because Barry highlighted that he would >>> benefit from it immediately [2]. There are no changes vs the version in that >>> series. >>> >>> It applies against today's mm-unstable (275d686abcb59). (although I had to fix a >>> minor build bug in stackdepot.c due to MIN() not being defined in this tree). >>> >>> Thanks, >>> Ryan >>> >>> >>> .../admin-guide/kernel-parameters.txt | 8 +++ >>> Documentation/admin-guide/mm/transhuge.rst | 26 +++++++-- >>> mm/huge_memory.c | 55 ++++++++++++++++++- >>> 3 files changed, 82 insertions(+), 7 deletions(-) >>> >>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt >>> index bcdee8984e1f0..5c79b58c108ec 100644 >>> --- a/Documentation/admin-guide/kernel-parameters.txt >>> +++ b/Documentation/admin-guide/kernel-parameters.txt >>> @@ -6631,6 +6631,14 @@ >>> : poll all this frequency >>> 0: no polling (default) >>> >>> + thp_anon= [KNL] >>> + Format: [KMG]:always|madvise|never|inherit >>> + Can be used to control the default behavior of the >>> + system with respect to anonymous transparent hugepages. >>> + Can be used multiple times for multiple anon THP sizes. >>> + See Documentation/admin-guide/mm/transhuge.rst for more >>> + details. >>> + >>> threadirqs [KNL,EARLY] >>> Force threading of all interrupt handlers except those >>> marked explicitly IRQF_NO_THREAD. >>> diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst >>> index 24eec1c03ad88..f63b0717366c6 100644 >>> --- a/Documentation/admin-guide/mm/transhuge.rst >>> +++ b/Documentation/admin-guide/mm/transhuge.rst >>> @@ -284,13 +284,27 @@ that THP is shared. Exceeding the number would block the collapse:: >>> >>> A higher value may increase memory footprint for some workloads. >>> >>> -Boot parameter >>> -============== >>> +Boot parameters >>> +=============== >>> >>> -You can change the sysfs boot time defaults of Transparent Hugepage >>> -Support by passing the parameter ``transparent_hugepage=always`` or >>> -``transparent_hugepage=madvise`` or ``transparent_hugepage=never`` >>> -to the kernel command line. >>> +You can change the sysfs boot time default for the top-level "enabled" >>> +control by passing the parameter ``transparent_hugepage=always`` or >>> +``transparent_hugepage=madvise`` or ``transparent_hugepage=never`` to the >>> +kernel command line. >>> + >>> +Alternatively, each supported anonymous THP size can be controlled by >>> +passing ``thp_anon=[KMG]:``, where ```` is the THP size >>> +and ```` is one of ``always``, ``madvise``, ``never`` or >>> +``inherit``. >>> + >>> +For example, the following will set 64K THP to ``always``:: >>> + >>> + thp_anon=64K:always >>> + >>> +``thp_anon=`` may be specified multiple times to configure all THP sizes as >>> +required. If ``thp_anon=`` is specified at least once, any anon THP sizes >>> +not explicitly configured on the command line are implicitly set to >>> +``never``. >> >> I suggest documenting that "thp_anon=" will not effect the value of >> "transparent_hugepage=", or any configured default. >> >> Wondering if a syntax like >> >> thp_anon=16K,32K,64K:always;1048K,2048K:madvise >> >> (one could also support ranges, like "16K-64K") >> >> Would be even better. Then, maybe only allow a single instance. >> >> Maybe consider it if it's not too crazy to parse ;) > > I prefer the current approach because it effectively filters cases like this. > > [ 0.000000] huge_memory: thp_anon=8K:inherit: cannot parse, ignored > [ 0.000000] Unknown kernel command line parameters > "thp_anon=8K:inherit", will be passed to user space. > > if we put multiple sizes together, 8K,32K,64K:always > > We can't determine whether this command line is legal or illegal as it > is partially legal and partially illegal. Besides: I wouldn't bother about this "user does something stupid" scenario that much. But yes, once we support more sizes a cmdline might turn invalid on an older kernel. However, I don't see the problem here. User passed a non-existant size. Ignore that one but handle the others, like you would with multiple commands? It can be well defined and documented. The command line is legal, just one size does not exist. The world will continue turning :) -- Cheers, David / dhildenb