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Received: from [50.53.43.113] (helo=[192.168.254.34]) by bombadil.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1vQ90E-00000004RVo-0I4R; Mon, 01 Dec 2025 18:52:02 +0000 Message-ID: <37934c20-4cf9-480f-847d-212e7efb350a@infradead.org> Date: Mon, 1 Dec 2025 10:52:00 -0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v13 mm-new 16/16] Documentation: mm: update the admin guide for mTHP collapse To: Nico Pache , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org Cc: david@redhat.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, dev.jain@arm.com, corbet@lwn.net, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, akpm@linux-foundation.org, baohua@kernel.org, willy@infradead.org, peterx@redhat.com, wangkefeng.wang@huawei.com, usamaarif642@gmail.com, sunnanyong@huawei.com, vishal.moola@gmail.com, thomas.hellstrom@linux.intel.com, yang@os.amperecomputing.com, kas@kernel.org, aarcange@redhat.com, raquini@redhat.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, tiwai@suse.de, will@kernel.org, dave.hansen@linux.intel.com, jack@suse.cz, cl@gentwo.org, jglisse@google.com, surenb@google.com, zokeefe@google.com, hannes@cmpxchg.org, rientjes@google.com, mhocko@suse.com, hughd@google.com, richard.weiyang@gmail.com, lance.yang@linux.dev, vbabka@suse.cz, rppt@kernel.org, jannh@google.com, pfalcato@suse.de, Bagas Sanjaya References: <20251201174627.23295-1-npache@redhat.com> <20251201174627.23295-17-npache@redhat.com> Content-Language: en-US From: Randy Dunlap In-Reply-To: <20251201174627.23295-17-npache@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4E6951C0010 X-Rspamd-Server: rspam06 X-Rspam-User: X-Stat-Signature: b1ckn79yo6c77qyqgm7ocgbnw69bwz33 X-HE-Tag: 1764615126-933356 X-HE-Meta: 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 p16cG6Ho 7HL0Y91+SWfqbKzp4eJ0G55YhfYX/ivng8WLvdSyyzEsrVW7XAdEJRWhro+bKttEKAglZpe+9PTTgm4BlocLJykdiAzjc14KkbEaH94TbNGWeZzgbtzrKn82k/JvMQ1DvOKkfXeP+QJSbqAAMQXzj4KrH7zOLqZv6eveBKmPRxCakLVM7GkKBeHanaPzx93cMAZ20ZOenbVeaAQYXmd7viwiGu05j27yRn4o5E7fV1iZ8As7lHThRCHImOb5ScDfiZ5bT07onaTb+GWCOGpkOsOmxruCPv8OU3Ub9rTYa2yfEmtV7JKY8/e1NeGA430/vQJB7BXkH9Mc+yTLB2Gt6hg28h7bC7pCdnnh4rPSjgRZ0E1F/1YLgFWs0V0/ueOWEEW9tZQnU8FIQNHbm/V1dzK3XzIxdcaXsCsTA 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 12/1/25 9:46 AM, Nico Pache wrote: > Now that we can collapse to mTHPs lets update the admin guide to > reflect these changes and provide proper guidance on how to utilize it. > > Reviewed-by: Bagas Sanjaya > Signed-off-by: Nico Pache > --- > Documentation/admin-guide/mm/transhuge.rst | 48 +++++++++++++--------- > 1 file changed, 28 insertions(+), 20 deletions(-) > > diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst > index d396d1bfb274..87bcfa80886a 100644 > --- a/Documentation/admin-guide/mm/transhuge.rst > +++ b/Documentation/admin-guide/mm/transhuge.rst > @@ -63,7 +63,8 @@ often. > THP can be enabled system wide or restricted to certain tasks or even > memory ranges inside task's address space. Unless THP is completely > disabled, there is ``khugepaged`` daemon that scans memory and > -collapses sequences of basic pages into PMD-sized huge pages. > +collapses sequences of basic pages into huge pages of either PMD size > +or mTHP sizes, if the system is configured to do so so. > > The THP behaviour is controlled via :ref:`sysfs ` > interface and using madvise(2) and prctl(2) system calls. > @@ -219,10 +220,10 @@ this behaviour by writing 0 to shrink_underused, and enable it by writing > echo 0 > /sys/kernel/mm/transparent_hugepage/shrink_underused > echo 1 > /sys/kernel/mm/transparent_hugepage/shrink_underused > > -khugepaged will be automatically started when PMD-sized THP is enabled > +khugepaged will be automatically started when any THP size is enabled > (either of the per-size anon control or the top-level control are set > to "always" or "madvise"), and it'll be automatically shutdown when > -PMD-sized THP is disabled (when both the per-size anon control and the > +all THP sizes are disabled (when both the per-size anon control and the > top-level control are "never") "never"). > > process THP controls [snip] -- ~Randy