From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 7983E1F16B for ; Fri, 12 Sep 2025 13:48:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757684886; cv=none; b=hpbQ+hb05OXlgefIJyn6ylAOIehlAJN2WlS9fVemwDQghX0SicpH3obJLJ22IReobVcC3bTRdGVgGMsL1NWSHhDFBJ3hq4dOWYthhVNLGOMCwkMEI7cEVrWZuxCgj6VL1SoZKkVcy8KOaWrzdWxkYHMu6cBc6WcrOziHCLUCd4I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757684886; c=relaxed/simple; bh=/ln5JGNWmfcCe8/H0oSeSbnsYQEmNVX3vWvsR1wlNjc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=iZY0/GGYAG+7onU4lN8wUC6NEXChwVMFJ/7ygkYvsIY/M+RHngQQAmWv9rKhF6wV0TYW6mR6iqMxxvHpkCGRLrwrptlQx5WfS2F7yE1ApiklJeDhyoZgfY9BiOpLMw3e9pWZvGYM/42n6i+qeA7dJtva5arWrvEPxByFjhOB87c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=grzuAL/T; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="grzuAL/T" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1757684884; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=w3448OdTgFs0YiOnfQSy1wV2L7Q5FFoX8LkMxHWDXQ0=; b=grzuAL/T9NeXhOU/e3E8Hk6xupxbklC21TUsry2qclH7fvSEbBLNvFvzQRzAvGbdAC8HjA Ttgc2Y0nEmM9OPfy4c7Cmo7048TSPworwfNQwNWc8M6mmGMnsl5jPH3WXJcYMi3eH3+Jag Qfijkj1QbntGfxgoniI24/8y9OLkGRY= Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-180-wu7dZxVpNVGzxWhfv-BfGQ-1; Fri, 12 Sep 2025 09:48:02 -0400 X-MC-Unique: wu7dZxVpNVGzxWhfv-BfGQ-1 X-Mimecast-MFC-AGG-ID: wu7dZxVpNVGzxWhfv-BfGQ_1757684881 Received: by mail-wr1-f69.google.com with SMTP id ffacd0b85a97d-3e2055ce8b7so898126f8f.0 for ; Fri, 12 Sep 2025 06:48:02 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1757684881; x=1758289681; h=content-transfer-encoding:in-reply-to:autocrypt:content-language :from:references:cc:to:subject:user-agent:mime-version:date :message-id:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=w3448OdTgFs0YiOnfQSy1wV2L7Q5FFoX8LkMxHWDXQ0=; b=xHBTNi3+MtIcIxTXwlQk/gOWV0kmowHQblosJY113rX+xbZDBg9NT34/mYwbuCghzE xgtiO0MvfixxPUjPyFWNYzBP7o/ehOAw8BLAD2fdC+oII1AtMZ1MBBTbRX+uA1qS4QKx fdC2vGJmlQpoDq2Ay55Lq2RbrjYHZ8E/44GuJIyMEAaT2hwudaZyp9NmpCIy+/NvhsxQ J+XHZaHbfs+5t6JYl0oE/24577nZ3ok9ggSKhfYTs7RmyU7cZ50EWOmvA1p6reDQWgzn fHn23UYFxyW9OoC9XRT0aw7PwBVnDHIrBh1wr1Agzw/PExXSNCmlBgPr7VP93H4Xyg4t G2Og== X-Forwarded-Encrypted: i=1; AJvYcCUR1cmTs8FIWph3qrWZ5mRBypgS2sTvdJDChiRzCDGHWURAG1NO/3C4qJ1KQcYKVLrNfjA7YsjR7YYQU/5NaJJA5SQ=@vger.kernel.org X-Gm-Message-State: AOJu0Yw6F4NZNPk6mUQYnT86/eF0qDRI7K3X8Nz6uhjJLY4+CpMY6sCB 2BpvSQ6bpu2f/s7mNgyn4z5//571xcDjhF/DdTg1oD/LZd11A5ANlfAiZN3xnG1V6WyhvcLeVF2 By/wo4kchBsrPIh7dWjUhhbUMCaZKxOr5OMddtJfzaK156GDs6SROEM93/DZnh0U19MHKRhHgCQ == X-Gm-Gg: ASbGncsIajmswMp4RnUSrX9QptWW1uOWqtAySypn26nJqNjlQMo8vvgexR2kp5HOe5T qgT/HZBeEyDA6EZTRyh187Ix6PT89deFO9sXAwSS09aEBceSPlQ+GG8jJrDPHZCC7axp1fzR81Q TO7k59qQF1mgnD6usPWurLUYlkRKtmUGTWu/bEOnSSaq3uOQgBbwOVv2UIM4RP4ElCdlgwVkqHG MMlQcKhs2lvfmDMIjWt7MY4uEtFQ6R6l012r4ZYJ/cs4ZAdU+qkzHHA69zOXew5XQVwYyjl5J3i V/7/D016ySWyixOXavvrrFQCICmgsLB2vyOD8txWjMmocwWLNdZXT89m/hoTnitTyqzDHsUBvC5 /DqpY6fCfaieBX4pgAY6+X0Deao0xRimCT/HDB1x/GucLB39AW2LIOxUE6w3Tvl9vp+o= X-Received: by 2002:a05:6000:2903:b0:3e0:152a:87b4 with SMTP id ffacd0b85a97d-3e7659db0ecmr2929899f8f.35.1757684881156; Fri, 12 Sep 2025 06:48:01 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHR3i6SRCrcMcssae1nGWwzt+oNV7vkhRgpzb3bl3dJ8CMEtAZfsOX+4eMBZZIz5FBmhHDpKA== X-Received: by 2002:a05:6000:2903:b0:3e0:152a:87b4 with SMTP id ffacd0b85a97d-3e7659db0ecmr2929876f8f.35.1757684880716; Fri, 12 Sep 2025 06:48:00 -0700 (PDT) Received: from ?IPV6:2003:d8:2f20:da00:b70a:d502:3b51:1f2d? (p200300d82f20da00b70ad5023b511f2d.dip0.t-ipconnect.de. [2003:d8:2f20:da00:b70a:d502:3b51:1f2d]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3e7607cd691sm6839560f8f.32.2025.09.12.06.47.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 12 Sep 2025 06:48:00 -0700 (PDT) Message-ID: <43f42d9d-f814-4b54-91a6-3073f7c7cedf@redhat.com> Date: Fri, 12 Sep 2025 15:47:58 +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 v11 00/15] khugepaged: mTHP support To: Kiryl Shutsemau , Nico Pache Cc: linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, 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, 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: <20250912032810.197475-1-npache@redhat.com> From: David Hildenbrand 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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: _TvVpgq4Mf73CM73Wh9gL61qRoBO89DuoSHs54V4vdo_1757684881 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 12.09.25 14:19, Kiryl Shutsemau wrote: > On Thu, Sep 11, 2025 at 09:27:55PM -0600, 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 do >> binary recursion on 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. When no mTHP size is enabled, the >> legacy behavior of khugepaged is maintained. max_ptes_none will be scaled >> by the attempted collapse order to determine how full a mTHP must be to be >> eligible for the collapse to occur. 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. >> >> When enabling (m)THP sizes, if max_ptes_none >= HPAGE_PMD_NR/2 (255 on >> 4K page size), it will be automatically capped to HPAGE_PMD_NR/2 - 1 for >> mTHP collapses 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. > > Hm. Maybe instead of capping at HPAGE_PMD_NR/2 - 1 we can count > all-zeros 4k as none_or_zero? It mirrors the logic of shrinker. BTW, I thought further about this and I agree: if we count zero-filled pages towards none_or_zero one we can avoid the "creep" problem. The scanning-for-zero part is rather nasty, though. -- Cheers David / dhildenb