From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 216AAE7BDA8 for ; Mon, 16 Feb 2026 12:15:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3CED26B0005; Mon, 16 Feb 2026 07:15:51 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 3A6BD6B0088; Mon, 16 Feb 2026 07:15:51 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 27B736B0089; Mon, 16 Feb 2026 07:15:51 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 0FBEF6B0005 for ; Mon, 16 Feb 2026 07:15:51 -0500 (EST) Received: from smtpin09.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id B461D160D47 for ; Mon, 16 Feb 2026 12:15:50 +0000 (UTC) X-FDA: 84450216060.09.F9652A4 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf16.hostedemail.com (Postfix) with ESMTP id 0E353180016 for ; Mon, 16 Feb 2026 12:15:48 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=AVXrh8Bj; spf=pass (imf16.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1771244149; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=SdYpqeQXImu32z4zZ0GX0vrUoE01wz/xIHP7g6aO/xg=; b=ZLo9h/r4KHfxWoGhW/b4+HGHbXBDvXxSM1Ga4l7bhtsfLpePpD+eHeM+m1eYA/HlUKoXQ7 een0mVkyqz2dZdfp8SfQS4m5Gm/Txy8coTfjarEDOzinkFZJaOWx3Z9pp0NZyjAEU34NEv hPl29lwJ9HXgf2+tlwEpcG7xj5G61BQ= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=AVXrh8Bj; spf=pass (imf16.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1771244149; a=rsa-sha256; cv=none; b=5STAmfbOVGMH+XvNGFB8yPMyU91D6jZrdIXD2VFT8BW1rpdZj3tsNf2JRfK1tnolHJyQsH J1x9WvnWOj2z18ufYA1SdGA02kWnUBVR8bgdrJ0pYdAlFiTEr2kA5KFln6+b+lM6PQa83/ oii5hr34cVQVfqat2Xgn8lH6VOuVg8c= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 695176012B; Mon, 16 Feb 2026 12:15:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 96160C19423; Mon, 16 Feb 2026 12:15:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771244148; bh=yVXbmrozFUX7lxzw8jVfric8iiV/l74dHezhvXM0gRY=; h=Date:Subject:To:References:From:In-Reply-To:From; b=AVXrh8BjTet237u9QvLtZKUMdQywnXodPYrNYJHMOvqIp8MvMHfnX3yh1Ss00Jka2 tHje6vzf9uu1aGurYdlX0NDkh5ooifFxOZFjreBPiplMSWImSxV0T69nX/FXgmva5M EYYET4JF1tZVWOZ3MANeLlUZ+SZd8wmk0byEkO1GgO5PSD6HY84j78C8aXtkjZoLNj zOg8SbK7r5sb9Llwaww3xS88RwCuD8cWCehRR15b4f/+31UhDGgbt8R6octtYObmHP fVTYLKlcaDgAQHUKROovHHfDm/H4sLYrvgZum5Ad03ATRfs8vagQDwODPp4s+Nvz4n ltZBXb7nZsceg== Message-ID: Date: Mon, 16 Feb 2026 13:15:43 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: Add AnonZero accounting for zero-filled anonymous pages To: Wenchao Hao , Andrew Morton , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260214084514.2842745-1-haowenchao22@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+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: <20260214084514.2842745-1-haowenchao22@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: 34p7bj7k7wg694pqgheuwzuqzd5bzkbo X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 0E353180016 X-HE-Tag: 1771244148-318453 X-HE-Meta: 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 oSzNpI44 j6zLGWXBFIMgcccCXF7/ftf7fKETiNo5nwFPazXRoWktEQmsvCtrBFDKhfAAkG4xBsCPB2sHG5ZNW67gqtMTGuVwkcuARbLY8BC3bmSqc3WgRU4l2pvkM+Ate+kFuA9rhYMo+HyvWROiAvap1KZXMrD+7K/l+4ljvSG651JA9Ri3K15yNhw5jZtsS2T05w8wLEhgBFOEeDLTGveNdQN4v4pPUtw+gBXWSirxZE/aiBf0SwboXiL0bBSwFA5swMVF04fg6K47f2hIp7YEKdMNWajCTqbshmvt08TAxcOzKXT1bWMo= 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 2/14/26 09:45, Wenchao Hao wrote: > Add kernel command line option "count_zero_page" to track anonymous pages > have been allocated and mapped to userspace but zero-filled. "count_zero_page" is rather sub-optimal parameter name. "anonzero_in_smaps" or sth like that? Still wondering if there could be a better way to enable this dynamically. In particular, not using a core parameter. If you use a module parameter, you can just set on the cmdline proc.anonzero_in_smaps=1 And dynamically set/observe it in /sys/module/proc/parameters/anonzero_in_smaps diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index d7d52e259055..0301b9cd28f8 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -34,6 +34,10 @@ #define SEQ_PUT_DEC(str, val) \ seq_put_decimal_ull_width(m, str, (val) << (PAGE_SHIFT-10), 8) + +static bool anonzero_in_smaps; +module_param(anonzero_in_smaps, bool, 0644); + void task_mem(struct seq_file *m, struct mm_struct *mm) { unsigned long text, lib, swap, anon, file, shmem; > > This feature is mainly used to debug large folio mechanism, which > pre-allocates and map more pages than actually needed, leading to memory > waste from unaccessed pages. > > Export the result in /proc/pid/smaps as "AnonZero" field. > > Link: https://lore.kernel.org/linux-mm/20260210043456.2137482-1-haowenchao22@gmail.com/ > Signed-off-by: Wenchao Hao > --- > Documentation/filesystems/proc.rst | 5 +++++ > fs/proc/task_mmu.c | 10 ++++++++++ > 2 files changed, 15 insertions(+) > > diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst > index b0c0d1b45b99..573c8b015e39 100644 > --- a/Documentation/filesystems/proc.rst > +++ b/Documentation/filesystems/proc.rst > @@ -545,6 +545,11 @@ replaced by copy-on-write) part of the underlying shmem object out on swap. > does not take into account swapped out page of underlying shmem objects. > "Locked" indicates whether the mapping is locked in memory or not. > > +"AnonZero" shows the size of anonymous pages that have never been accessed > +after mapping, and it can reflect the memory waste caused by huge pages. That's not correct. They could be read/written, but with zeroes. > +Implemented by scanning the size of zero-filled pages of the VMA. It > +is default disabled, and enabled via cmdline param "count_zero_page=true". Probably best to keep it simpler: "AnonZero" shows the size of anonymous pages that contain zeroes. Zero-filled pages can indicate memory waste caused by memory-overallocation with (m)THPs. Availability is controlled through XYZ. -- Cheers, David