From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 4BE1F33A6F2; Fri, 22 May 2026 21:52:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779486730; cv=none; b=rUXevWxjkI6REoLyki19ED2OWMqX0nkiojnz7MWFiXCiZb4c4gh+MqWDgWydrz01PtSxB7cVIP1fX+6lfEGGP+GI469K+TgZy2xARYsN8uNnX/E90kRNWtZlJkXlG1QZBKKemIr8C2RpP+Dg2VWaofbyUkeYE5tSL6T2Sqlmx/c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779486730; c=relaxed/simple; bh=X0hD17+JbLsaNSa9yY/2I/Yjtt5uiV14riR3BO6HEo0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=if4LJDsBTtwJPRQt9mfX/IpGCPrj0XX3deeFi30UJHlQZJ/SkAPLKu6O3KIa4l7IBzqhZYHMt8iUJPX/NqqOrvl7+6lUiegIbYo/JNnVW8GUIhe0Ovqdm+wK1bAi+12yf9O8R/N9Ac7oOc+JMOSIu9CfGIaItNRc+JqTx/ZFI1w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GBit5RGA; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="GBit5RGA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E47E11F000E9; Fri, 22 May 2026 21:51:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779486728; bh=eApYXU+swQ/aSMT4+a9qbCpi/b8FjdNDOxy/EU7ZU2c=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=GBit5RGATOfbr5x1B8Iah9ZKcHyEC4nw1LQkzGQ1ljV+PUlp0sDeFbRMge8ndkD2N 5hbxQmyDKoxzBT2A2WOm3msxhnQSIeFA1rxJEhBh1tS5fsrRP34troIl8gB8dwVSSy n7incecVx0eMXZzVx1M2WyuUX2wzl1KEGQyLqwcbXO5cLbzciDNnFyGrRMSJQ6Iv3u in+lJV5CbLbY5Vjz8OaHzoxOFZhQr3IBXF8Ojv4ugrXTIjR/CA64ZAImWeduGj97uq OswYEX7Pt1D2sTAFTHfmYgA4cGgJINi19f3moklhfuUcALrBsmn1Fmc4GXGXoVGWPL o6612VYwIJr7A== Message-ID: Date: Fri, 22 May 2026 23:51:52 +0200 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 mm-unstable v18 07/14] mm/khugepaged: skip collapsing mTHP to smaller orders To: Nico Pache , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org Cc: aarcange@redhat.com, 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, 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@infradead.org, 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, Usama Arif References: <20260522150009.121603-1-npache@redhat.com> <20260522150009.121603-8-npache@redhat.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/22/26 17:00, Nico Pache wrote: > khugepaged may try to collapse a mTHP to a smaller mTHP, resulting in > some pages being unmapped. The "some pages being unmapped" part is unclear. I assume what you mean is "possibly resulting in a partially mapped source folio, which is undesired." But there is also the problem that we could try collapsing a folio to a same-sized folio, which doesn't make sense (assuming the folio is fully mapped). Clarify all that, please. Acked-by: David Hildenbrand (arm) -- Cheers, David