From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 997A47DA66; Thu, 8 Jan 2026 16:10:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767888602; cv=none; b=A+g+25MjrxSlcJhx7KHzvMNc1Cv+JzjDg2APqn9xcETkWfkwAicIBqgnf4JM7tiLonCdYQ84ZwR7Niq5Xc/NldJdIRs/lcHXEB1UpC2aijAMz3TRIKc9Nf1O/5/0MtgJkdeDB6ARzkcyDdgxQXRf3+EVIeGsipQgngJY9PScmBM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767888602; c=relaxed/simple; bh=KqKzdFoLZFct6ZLIwpLIWMBiFuKLvoaOI3xqdCwiEmc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=uRECp15B0ylffY6HCqv+b+5pbOSn/f8ni6GzMVSGHBaBNY+Oa4BXzhEFck6HMutPcViVsRYNcf/9NOITILdG3k4sCqtdEu9bZ6YIOv/dvlLknSSn7uVhySr2EtIWJkdmufpnjhJU4NzilzXe1reaJAdElt/lf5z3pqhshge9XjM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=uqXZJF63; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="uqXZJF63" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9BB0AC116C6; Thu, 8 Jan 2026 16:09:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767888602; bh=KqKzdFoLZFct6ZLIwpLIWMBiFuKLvoaOI3xqdCwiEmc=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=uqXZJF63sweS9rbp4xNKKiVg6CPHseMPnaKDYO7JRf+hWWLkRcZLC3YNj692EulQy JCMsfOkFmyb3VbWv/eztxY30WQKamopYAS9ENw41MX6rhf79onZJeqhESKv8qhDrYT K3ongKIWUSpOS0fbSOAiFXgCDIxb0Ct0NRw8s4iBDAC9zLCQmCubgR8FDEA1Wki5B9 6VKIx2xQsRsEOFFEcEXTxp1iwYm1yWP1OQZUF8pNU9rgTq7m+df0TZ/pywau9QWp9g LWvLJQxkqT/wy1VwyV1CcxhAHZQRoymaD09kZfIruhwYSgIq6rfpMW5qpRdmP0dcIZ B6IXqXneBfmew== Message-ID: Date: Thu, 8 Jan 2026 17:09:49 +0100 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v13 mm-new 00/16] khugepaged: mTHP support To: Nico Pache , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org Cc: 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, rdunlap@infradead.org, hughd@google.com, richard.weiyang@gmail.com, lance.yang@linux.dev, vbabka@suse.cz, rppt@kernel.org, jannh@google.com, pfalcato@suse.de References: <20251201174627.23295-1-npache@redhat.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 12/1/25 18:46, Nico Pache wrote: > The following series provides khugepaged with the capability to collapse > anonymous memory regions to mTHPs. > > To achieve this we generalize the khugepaged functions to no longer depend > on PMD_ORDER. Then during the PMD scan, we use a bitmap to track individual > pages that are occupied (!none/zero). After the PMD scan is done, we use > the bitmap to find the optimal mTHP sizes for the PMD range. The > restriction on max_ptes_none is removed during the scan, to make sure we > account for the whole PMD range in the bitmap. When no mTHP size is > enabled, the legacy behavior of khugepaged is maintained. > > We currently only support max_ptes_none values of 0 or HPAGE_PMD_NR - 1 > (ie 511). If any other value is specified, the kernel will emit a warning > and no mTHP collapse will be attempted. If a mTHP collapse is attempted, > but contains swapped out, or shared pages, we don't perform the collapse. > It is now also possible to collapse to mTHPs without requiring the PMD THP > size to be enabled. These limitiations are to prevent collapse "creep" > behavior. This prevents constantly promoting mTHPs to the next available > size, which would occur because a collapse introduces more non-zero pages > that would satisfy the promotion condition on subsequent scans. > > Patch 1: Refactor/rename hpage_collapse > Patch 2: Refactoring to combine madvise_collapse and khugepaged These two patches could get queued already separately, right? -- Cheers David