From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 DC231267F51 for ; Mon, 24 Feb 2025 16:56:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740416210; cv=none; b=Ew53lPXGTIXwxemcoNVfZ9gbCgVVsVtiDChjerQMwxjOIiMB0EyEvSKidOIGb03nIx2ybFYo67iG2td4LnMwZXPxHeGxBIbbRMnU9rtX6zcZVYT7C1JxuLtfGigAR1484qKIBwltxxfFv+oHaks9lSf67a7NqyWjfRruJn/zKdU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740416210; c=relaxed/simple; bh=qpkZkgDQSCpDOrawHj8ee8It7p8kTmPkI0TP7miUP/A=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=bPmf6o1995JMGAeeAluG2Ikg9iu4XIYxkL5TznFQ9t+33eecfyoNcir7uo/lRx62a2wWE+S07OWB25I+T6UgG3hJBQGmCCfMk6o8cfI1iEsCDebac8itdfrPm+89UfmkenliRpRt0GHcPWMpD4wucf2EMEhSsRQmjiqhQdQwShw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none 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=cQBZEO/H; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none 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="cQBZEO/H" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1740416207; 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=4IIiK38txs39RTm2yNSD9uzsg2Epj+W/QUBXdJN6a7s=; b=cQBZEO/HEWkYeTdP2CO4KjGQ5YAiQ5IkdofFEiizbarbA1mtRXRO5TMeFXnpXyWQU1CTGz ZtKhv/UOpzYSW/8ByUjFSg5CHexRmbt9976dqTpzVKBxC66yEcBCEjfZTalg6yQAGScTDl xH+TOBaG7mx59npqjdPAmCoAViVpEK8= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-623-cFcvkLqDO869_OW0DIssVQ-1; Mon, 24 Feb 2025 11:56:45 -0500 X-MC-Unique: cFcvkLqDO869_OW0DIssVQ-1 X-Mimecast-MFC-AGG-ID: cFcvkLqDO869_OW0DIssVQ_1740416204 Received: by mail-wr1-f72.google.com with SMTP id ffacd0b85a97d-38f2c0aa6d6so2512394f8f.0 for ; Mon, 24 Feb 2025 08:56:45 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1740416204; x=1741021004; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=4IIiK38txs39RTm2yNSD9uzsg2Epj+W/QUBXdJN6a7s=; b=tEB4gsvj2YhDorxIBZv2g19QxWOAH0E3EONheEzoCkbytK/Gyr5XyhTqU/JlteR7+Z 5guvD0piWzPvSHqGvTR68HKDPKJb1ZcdmaH8KhV+B6CKqB2w23LprGBJcg5TzlLekPeP nWtfBYHQXqWbCWlKLBTtQHBmerVVMXOyCbWSHQHt1q5j0v9R3YJVSS2C+58dczqyPsc3 Itcyyb8XO0FXB/DcO5ldZO3rKbab4k6O5S82QJjuA5Xm88njFMv5C3tpOeekLJeU10wR Vv5l39Tz41Y0y5M4QcWI5TVgqbOT2wNMjyb2So3hMmWjNkVtX2DeuzuZ8617MaPq6n4G 0jjw== X-Forwarded-Encrypted: i=1; AJvYcCWYj5WJtikWs2k3B2qYN8VfyRhCXFpYfvOyErP5g5M2wD3Kh3crrNkP5W53HZubrlAfscStfozryxs=@vger.kernel.org X-Gm-Message-State: AOJu0YwdxtR9WuCuoaZZ6YabQoLF2RvSTGJ+QlRvFltHtv+/FtBMTWag kl0rCCW10jKZYk27NlgLBsNoymiRXebVFz6klyhlG244Def02EYXVqtm/4lg/oMTZzg3jkxtsFS 0iOzqL9MqGyHqG6W4j9942+wbZGQxCQy3P5jpVutvkk9akNoCrXfnfb3xug== X-Gm-Gg: ASbGncsShq/ppj7zBBX39BNSIgrc36XD6W6vrv2eR/fEebb1tsfKWkn631tZ980lv1U +ocFje1XuaO29KfHPFhCLKFEEqsD7tJg9CurY3bsa5kNBsJrAsDbVt/4AddLzhCSi1UVtquIMXz a72NZywFsGklJHs8zTucsAi7PBbbZJV4g7c6n/cOLAYTTXE/BOVTSvG/5ln5jWdWnyrvEnPG6HW Gpq9BRSRXiJydmcdTbwgTCf5yFMVG3haFlw9+PCjq3+ZwMRaHom+VI+9eLHDI8nloX11wv53Iev v3+rI+UZI+6tnCrH5WfG0Sdb5BH8O95gqFT19EseEg== X-Received: by 2002:a5d:5f90:0:b0:38d:c6b8:9fe1 with SMTP id ffacd0b85a97d-38f6f51d885mr12699064f8f.24.1740416204110; Mon, 24 Feb 2025 08:56:44 -0800 (PST) X-Google-Smtp-Source: AGHT+IHr48iDkbeT3BD6T31jawE7AoIz4aDQ8fc4EtI1CIkHNhBzvnREnXgHgZXA/JhJC2+PnfKZ2A== X-Received: by 2002:a5d:5f90:0:b0:38d:c6b8:9fe1 with SMTP id ffacd0b85a97d-38f6f51d885mr12699040f8f.24.1740416203760; Mon, 24 Feb 2025 08:56:43 -0800 (PST) Received: from localhost (p4ff234b6.dip0.t-ipconnect.de. [79.242.52.182]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-38f25914171sm32572475f8f.53.2025.02.24.08.56.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 Feb 2025 08:56:43 -0800 (PST) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-doc@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, David Hildenbrand , Andrew Morton , "Matthew Wilcox (Oracle)" , Tejun Heo , Zefan Li , Johannes Weiner , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Jonathan Corbet , Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Muchun Song , "Liam R. Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn Subject: [PATCH v2 18/20] fs/proc/task_mmu: remove per-page mapcount dependency for "mapmax" (CONFIG_NO_PAGE_MAPCOUNT) Date: Mon, 24 Feb 2025 17:56:00 +0100 Message-ID: <20250224165603.1434404-19-david@redhat.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250224165603.1434404-1-david@redhat.com> References: <20250224165603.1434404-1-david@redhat.com> Precedence: bulk X-Mailing-List: linux-api@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Let's implement an alternative when per-page mapcounts in large folios are no longer maintained -- soon with CONFIG_NO_PAGE_MAPCOUNT. For calculating "mapmax", we now use the average per-page mapcount in a large folio instead of the per-page mapcount. For hugetlb folios and folios that are not partially mapped into MMs, there is no change. Likely, this change will not matter much in practice, and an alternative might be to simple remove this stat with CONFIG_NO_PAGE_MAPCOUNT. However, there might be value to it, so let's keep it like that and document the behavior. Signed-off-by: David Hildenbrand --- Documentation/filesystems/proc.rst | 5 +++++ fs/proc/task_mmu.c | 7 ++++++- 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst index 09f0aed5a08ba..1aa190017f796 100644 --- a/Documentation/filesystems/proc.rst +++ b/Documentation/filesystems/proc.rst @@ -686,6 +686,11 @@ Where: node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page size, in KB, that is backing the mapping up. +Note that some kernel configurations do not track the precise number of times +a page part of a larger allocation (e.g., THP) is mapped. In these +configurations, "mapmax" might corresponds to the average number of mappings +per page in such a larger allocation instead. + 1.2 Kernel data --------------- diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 80839bbf9657f..d7ee842367f0f 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -2862,7 +2862,12 @@ static void gather_stats(struct page *page, struct numa_maps *md, int pte_dirty, unsigned long nr_pages) { struct folio *folio = page_folio(page); - int count = folio_precise_page_mapcount(folio, page); + int count; + + if (IS_ENABLED(CONFIG_PAGE_MAPCOUNT)) + count = folio_precise_page_mapcount(folio, page); + else + count = min_t(int, folio_average_page_mapcount(folio), 1); md->pages += nr_pages; if (pte_dirty || folio_test_dirty(folio)) -- 2.48.1