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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1776699422; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=bhKXz21irPByGBa7VXYiJn8tYPqBAC8fQ5GrPsI59Tk=; b=TolJBDx7xE/H9YRYEOaaa2c59QbAENz915P8NEt1sDN2YLJOzN6LkfmvImpF9Dh5/0Xs6+ gf9i+ca+ZqcN2IT85QX0vNIVoGwAprWrxdRqy8IuT2/vM2+BprjQmXu6llX+CEoU0R5Swi XILVICuLYFXBJDmwoW5IMq2RfMhlvs8= From: Usama Arif To: Nico Pache Cc: Usama Arif , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, akpm@linux-foundation.org, anshuman.khandual@arm.com, apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, byungchul@sk.com, catalin.marinas@arm.com, cl@gentwo.org, corbet@lwn.net, dave.hansen@linux.intel.com, david@kernel.org, dev.jain@arm.com, gourry@gourry.net, hannes@cmpxchg.org, hughd@google.com, jack@suse.cz, jackmanb@google.com, jannh@google.com, jglisse@google.com, joshua.hahnjy@gmail.com, kas@kernel.org, lance.yang@linux.dev, Liam.Howlett@oracle.com, ljs@kernel.org, mathieu.desnoyers@efficios.com, matthew.brost@intel.com, mhiramat@kernel.org, mhocko@suse.com, peterx@redhat.com, pfalcato@suse.de, rakie.kim@sk.com, raquini@redhat.com, rdunlap@infradead.org, richard.weiyang@gmail.com, rientjes@google.com, rostedt@goodmis.org, rppt@kernel.org, ryan.roberts@arm.com, shivankg@amd.com, sunnanyong@huawei.com, surenb@google.com, thomas.hellstrom@linux.intel.com, tiwai@suse.de, usamaarif642@gmail.com, vbabka@suse.cz, vishal.moola@gmail.com, wangkefeng.wang@huawei.com, will@kernel.org, willy@infradead.org, yang@os.amperecomputing.com, ying.huang@linux.alibaba.com, ziy@nvidia.com, zokeefe@google.com Subject: Re: [PATCH 7.2 v16 06/13] mm/khugepaged: skip collapsing mTHP to smaller orders Date: Mon, 20 Apr 2026 08:36:40 -0700 Message-ID: <20260420153641.215894-1-usama.arif@linux.dev> In-Reply-To: <20260419185750.260784-7-npache@redhat.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: o4qgxmcqb34xpymz4qopaasy8rsnyz53 X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 2ED404000D X-HE-Tag: 1776699424-531638 X-HE-Meta: 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 0BAMKB8m zJjLnpQalN3Gr9meNl10v53/FLVJY5xDZGkfvMsOtmjbzaFgG7AZTffK+8XCXgrgU4WAjYJugSH1bTdZ4+0HencHsVXPRHWM655Kj19l2nzl1qaaRCz3NGJw3d59FsR4HDU1bWAsostH46uXjLBMJ5r6IjA6aEY4yuI1uRNv3WzDpE7v3ibVhz0/XXHlyWZretnD2tWwc+kdciTxqNmNwnJnbetKe2lFCU0wkYKZySMrmFq0qOI3J8SRHG3Ij9hgw7rRSMUhlFyfaXLB9UGLwDAuLNsThQxlXXlGpeZr1Uv4uBkEmRI4kNHvceC9D9pSyVZPs6dKny0B0WNtuV3KuzL8QOaMdjYUHFUdzSHNP0DzGqVAOP7OZKSujylxtZBX1ieNyoKLaApXzL40= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, 19 Apr 2026 12:57:43 -0600 Nico Pache wrote: > khugepaged may try to collapse a mTHP to a smaller mTHP, resulting in > some pages being unmapped. Skip these cases until we have a way to check > if its ok to collapse to a smaller mTHP size (like in the case of a > partially mapped folio). This check is also not done during the scan phase > as the current collapse order is unknown at that time. > > This patch is inspired by Dev Jain's work on khugepaged mTHP support [1]. > > [1] https://lore.kernel.org/lkml/20241216165105.56185-11-dev.jain@arm.com/ > > Reviewed-by: Lorenzo Stoakes > Reviewed-by: Baolin Wang > Co-developed-by: Dev Jain > Signed-off-by: Dev Jain > Signed-off-by: Nico Pache > --- > mm/khugepaged.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > Acked-by: Usama Arif