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 E7F67C982DC for ; Fri, 18 Sep 2026 11:58:17 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D53B56B008A; Fri, 18 Sep 2026 07:58:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D04BD6B008C; Fri, 18 Sep 2026 07:58:16 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BF29C6B0092; Fri, 18 Sep 2026 07:58:16 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 995A56B008A for ; Fri, 18 Sep 2026 07:58:16 -0400 (EDT) Received: from smtpin26.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 30F0280680 for ; Fri, 18 Sep 2026 11:58:16 +0000 (UTC) X-FDA: 85226734992.26.E2B6016 Received: from mail-wr2-f12.google.com (mail-wr2-f12.google.com [74.125.225.76]) by imf31.hostedemail.com (Postfix) with ESMTP id 659EE20003 for ; Fri, 18 Sep 2026 11:58:14 +0000 (UTC) Authentication-Results: imf31.hostedemail.com; dkim=pass header.d=gmail.com header.s=20251104 header.b=oTQHI4N4; spf=pass (imf31.hostedemail.com: domain of kmanaouil.dev@gmail.com designates 74.125.225.76 as permitted sender) smtp.mailfrom=kmanaouil.dev@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1789732694; h=from:from:sender: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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=PPJuKezU+0LGqyieR7K4QMTdZgLRjpBWSmFo8vmzfNc=; b=d9szNR71wcKBa0yT/SGIO1BHiujZhPx62MCbmAaawHvp5hWe2nmAEn0PQ72uezyUa8JcVF t1SURX7QpNLSbiq0S8El/QK4KQxeRE6t8AA7sKkQ63diS/LUsYZsOgFIMgKGTtKjtklDOv sNAlfQ6DD3RAI8wsC8/uDmYwtvhjAQs= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1789732694; b=3wFhyVFF307H+tmRcR2nyGnSWnoIjIGCCZdiQYYXxDWGlGFbNvrf+rdjJAas3eLw6fqIOR tX1/NQ/oeZ837ZsYIbbk85ta8pGIGfeq4RbjKPYku1/GPeembvo3N2ZCymm3k0B0BACT0Y 20Y5bO5RmXdhbqYkOGsYMP+ZvQ8f2HQ= ARC-Authentication-Results: i=1; imf31.hostedemail.com; dkim=pass header.d=gmail.com header.s=20251104 header.b=oTQHI4N4; spf=pass (imf31.hostedemail.com: domain of kmanaouil.dev@gmail.com designates 74.125.225.76 as permitted sender) smtp.mailfrom=kmanaouil.dev@gmail.com; dmarc=pass (policy=none) header.from=gmail.com Received: by mail-wr2-f12.google.com with SMTP id ffacd0b85a97d-4843f22dcb8so461733f8f.0 for ; Fri, 18 Sep 2026 04:58:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1789732693; x=1790337493; darn=kvack.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=PPJuKezU+0LGqyieR7K4QMTdZgLRjpBWSmFo8vmzfNc=; b=oTQHI4N4GoTBKBqe6XyZ+YOXrBpJCcESGtoM13GD2EZaOmlqbwpi/jBue/+OSuD4W1 vPQnXH0qAbKVZR0foT+6ZVmyIXaZKnVcXt5gvKN+UmySRwoFIDmpBNlSyHC4Suu6tmEM 4ZjuW3Z/TWTDGxuY/TlVgxn1/1H5dn3OZnd7BBomBeqncjOozfqyyh5tiMbvfLtsYBek vTrT60C6wwtxMDYg2b1Ll3KEQR7jYOmanTjM1H0UPtfGSskXm8cfc018SEJQz/5Gahwb Jyy/kK6wAu7npDr32uMRqK13s/M7qrf+3QZG4UD81eapTlT1fgV2/20fGzVvSrXtCKkp a+HA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1789732693; x=1790337493; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=PPJuKezU+0LGqyieR7K4QMTdZgLRjpBWSmFo8vmzfNc=; b=kSzBdiAkz17/p3/ouL6zMCtZjhF5WNiMOdnpPV5J7Ccn+GR7TQ8NivHWUmCvpoI4z1 1IpNG5jmca5e8jjyUf+UlUUz/rF3nFq0aKm8zU/Ih+duW2CwQU0jLs6grO0vgp92syyB ru06cEheZHktd47j8IEyZiQHPtgcU3kiZ+d0FX9sARohbp4fv+KfbdO39n6XJtPLN2Bv s0V6KMS5SbrKpoBi73udfb5O3XKuuL4lK3+7ToCt6ksLc5L1pjLmPSrM3yShqbhXYOai bnit/eNRBLA3MGr+mTjsI4tgIa0SDvjiesV+9p5KQ6SyX+HNo/VUXs2do9d0xbHDnsX2 Bo/w== X-Forwarded-Encrypted: i=1; AKwUvBwRTCPGC5Us8TMDf9F6MSCgIqtBcT5FUufWL49SzEQsw0wtB2WT6SvSkEBLN1F2OrguTVXBRYsp4g==@kvack.org X-Gm-Message-State: AFuF++n6GTFazv53ayFT47G/RdsPcR15CFXeb6Lvma3CwBIbuZ7IYD/y uPDuMg0QOPeZ8ShzT/nMCiTYvFvaV6xcJdUQu1qgLI33D7JSQCQZ7Xei X-Gm-Gg: AYBFou0OY8G2ETUxwWKC6JjO8HlZMUYOOsHS5n4eqnui38WAD7Si1DgWnwXQtlwnY0U 4ziZ1sc+4wjMspeu6P/fx9kKMWTcsnPDesycaX1gRjyx9EFN/66YSVhHY1D5swVNJ3iLtHZ3GUU GR2Pc4B2zPeUvxtATZYVcpGVr87h+o02Ulv8XElqXhO43E2CZVDpyUljqQ/ITiaPP31EfMTlmAR GlbmCug4g22QXFPT48V0NBiCoTVrr/oLMgA7lmrFKYN8EqvL+dGWaE0bGEXtnHDV9aqrszh9XLS HdCu9qx5dqXXTTJJPlPwdl5V7XJFn7gh0rqkGiABMyaLM3IvsnIPebFxwhP2eg1LG0UYJ8fiqfo X4Y6BfcGBJQmwRQvGMXPrwkNuYYEkUGXm2bIgbgbdRoS2vadxZs6gHSNZmzP2QBNbl+r9Tg6L6p /LlDboIMiRn9/6EX853T3K5C5ciN0dJlMiVbcNgiYSuXGGLyiFxLoJoPPhP3yWgcY7uPdhhO2Vr HxEaj3Gs5ueDHZOU7xLOrySUcdQRZCPilIWR0FLZPlKA9SpCn+CIIMv0kt/ERLpH7ERuVB7 X-Received: by 2002:a05:6000:184a:b0:486:e300:a0c3 with SMTP id ffacd0b85a97d-4871e212306mr3249545f8f.12.1789732692470; Fri, 18 Sep 2026 04:58:12 -0700 (PDT) Received: from localhost (pat-125-254.wlan.net.ed.ac.uk. [192.41.125.254]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-487203f077fsm3145025f8f.26.2026.09.18.04.58.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Sep 2026 04:58:12 -0700 (PDT) Date: Fri, 18 Sep 2026 12:58:03 +0100 From: Karim Manaouil To: Bo Zhang Cc: akpm@linux-foundation.org, vbabka@kernel.org, david@kernel.org, surenb@google.com, mhocko@suse.com, brendan.jackman@linux.dev, hannes@cmpxchg.org, ziy@nvidia.com, ljs@kernel.org, liam@infradead.org, rppt@kernel.org, qi.zheng@linux.dev, shakeel.butt@linux.dev, kasong@tencent.com, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, zhaonanzhe@xiaomi.com, lipengfei28@xiaomi.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 4/4] mm: adjust free_pages to make __zone_watermark_ok() mTHP-aware Message-ID: <20260918115803.55bfl7whbvc5q25u@wrangler> References: <20260917171642.b4pkhqmvjwnq3vmq@wrangler> <20260918024238.31128-1-zhangbo56@xiaomi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260918024238.31128-1-zhangbo56@xiaomi.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 659EE20003 X-Stat-Signature: n1nqy36um88eyt5okntndj16echb4rp9 X-Rspam-User: X-HE-Tag: 1789732694-18137 X-HE-Meta: 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 eTuwSJM/ 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Sep 18, 2026 at 10:42:38AM +0800, Bo Zhang wrote: > On Thu, Sep 17, 2026 at 06:16:42PM +0100, Karim Manaouil wrote: > > > + if (READ_ONCE(huge_anon_orders_always) && order == compact_hpage_order()) { > > > + unsigned long free_pages = 0; > > > + > > > + for (int o = order; o < NR_PAGE_ORDERS; o++) > > > + free_pages += zone->free_area[o].nr_free << o; > > > > I understand that you don't need a precise value here, but in every > > instance in the kernel source tree where nr_free is accessed, it's > > accessed under the zone lock. Do we need to use READ_ONCE()? > > Good point, thanks. The nr_free read here is an intentional lockless > estimate. I'll annotate it with data_race(), matching how > fill_contig_page_info() in mm/vmstat.c reads the same > zone->free_area[].nr_free field without the zone lock: > > free_pages += data_race(zone->free_area[o].nr_free) << o; > > data_race() documents the intended racy read and keeps KCSAN quiet. > Happy to use READ_ONCE() instead if you'd prefer. Yeah, data_race() is probably a good starting point. Thanks! > Bo -- ~karim