From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D0365606A319 for ; Tue, 20 Oct 2026 01:16:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=3oaRtzn5; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=ibnw2b6Z DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Reply-To:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:Date: Content-Transfer-Encoding:Content-Type:References:In-Reply-To:To:Subject:From :Message-ID:Cc:MIME-Version:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=jOZ6xK7gPKz+7mr2Ctq9XJ42zWxJ6XJWSknxthBp88M=; b=3oaRtzn5eVaPZMYZNtpDKQMluN MRcWeLvX3iRGl1vRGk0XbJk9u4TMQ9eHmdnCxOe4t3MzpXOGAyGtHsaDfXgYwZ/HEKDmxeEY5bNMr LfX+zywNJGaQLTLg3JrEQSx83yo1FpxU2qnu9vHn7Pv5poAs5ughsr9wHljHWVNlfCTg2i02eborE W3+ts+SpTT9FNgZ12JSm58GT4Qxd55QjyzflhsXMXNQE6n+2lMiEMbTyrpGy/WFIo6NWQc4hTxsc0 co8OhpTBnh6G49zYRSAuv2bOMLNXPQg7kchn3Xfao2TKu2ZVZ3UslyHDDpoNcLBtC5H1klIYTrvkB 3xqDlKMg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xIySW-00000008bU4-19dP; Tue, 20 Oct 2026 01:16:08 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1xIyST-00000008bRZ-0J8C for kexec@lists.infradead.org; Tue, 20 Oct 2026 01:16:05 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id C3ED741262; Tue, 20 Oct 2026 01:16:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 75B881F000C4; Tue, 20 Oct 2026 01:16:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792458964; bh=jOZ6xK7gPKz+7mr2Ctq9XJ42zWxJ6XJWSknxthBp88M=; h=From:Subject:Reply-To:To:In-Reply-To:References:Date; b=ibnw2b6ZA7nuemzUk6cZUflsY9eR9KsWpFGzsQfYyVkfJsJYvbGyZxSvTDmFl7W89 rLRQc8K4a6ObmWafEkfjijW3WYVATjT8m+OOYFuoUNwhSD081wMEQgpAZ8yZwxnZma Gq3PiPpY+X2CX9fUoJSiFPLNLKIRzl17gtUWx2NcK9qwHdp3tXMi5rvHjDVRvBKDkF 3/gWsyXQUoUZOh1Q0iQhYso+GpXF0BNYQQhE+Ctkr5+xDcT8UhGlzwnqJrmK7KkLQ0 KbNMJ9jjygr4W4KTWBwlQt9ckTGT7MbB3q82csckRE/2Wj/TUCI0dGkEMu0UZVRJiR tWKpJoBNDvaKg== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v2 8/8] mm/vmstat: Avoid redundant per-CPU stat_threshold writes in refresh_zone_stat_thresholds() To: "Pasha Tatashin" , kees@kernel.org, rppt@kernel.org, juri.lelli@redhat.com, nik.borisov@suse.com, tglx@kernel.org, vschneid@redhat.com, kprateek.nayak@amd.com, vincent.guittot@linaro.org, bp@alien8.de, jpoimboe@kernel.org, tony.luck@intel.com, david@kernel.org, mingo@redhat.com, akpm@linux-foundation.org, seanjc@google.com, ljs@kernel.org, zhangguopeng@kylinos.cn, dietmar.eggemann@arm.com, mhocko@suse.com, vinicius.gomes@intel.com, vbabka@kernel.org, peterz@infradead.org, surenb@google.com, hpa@zytor.com, x86@kernel.org, dmatlack@google.com, tim.c.chen@linux.intel.com, kexec@lists.infradead.org, pratyush@kernel.org, dave.hansen@linux.intel.com, rostedt@goodmis.org, gmonaco@redhat.com, jgross@suse.com, mgorman@suse.de, graf@amazon.com, liam@infradead.org, ridong.chen@linux.dev, blum@kernel.org, longman@redhat.com, bsegall@google.com In-Reply-To: <20261019011446.834487-9-pasha.tatashin@soleen.com> References: <20261019011446.834487-1-pasha.tatashin@soleen.com> <20261019011446.834487-9-pasha.tatashin@soleen.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Tue, 20 Oct 2026 01:16:02 +0000 X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: sashiko-reviews@lists.linux.dev Sender: "kexec" X-Spam-Status: No, score=-11.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 X-Archived-By: > During CPU hotplug, vmstat_cpu_online() and vmstat_cpu_dead() invoke > refresh_zone_stat_thresholds() on every CPU transition. Currently, > refresh_zone_stat_thresholds() first zeroes > per_cpu_nodestats->stat_threshold across all online CPUs and all online > nodes, and then unconditionally writes per_cpu_zonestats->stat_threshold > and per_cpu_nodestats->stat_threshold inside the zone loop for every > populated zone and every online CPU. >=20 > However, calculate_normal_threshold(zone) only changes when > fls(num_online_cpus()) changes (at powers of 2) and is clamped at 125 > for large normal zones (>=3D 16 GB) once num_online_cpus() >=3D 64. > Unconditionally zeroing and rewriting every CPU's per-CPU stat_threshold > on every hotplug step repeatedly dirties remote per-CPU cachelines with > identical values (and briefly exposes stat_threshold =3D=3D 0 on live CPU= s). >=20 > [ ... ] > Total: 3.46 s -> 3.38 s (-2.3%) > refresh_zone_stat_thresholds() (cpu511 offline / online): > 104.6 us -> 50.7 us (-51.6%) / 109.3 us -> 53.5 us (-51.1%) >=20 > Signed-off-by: Pasha Tatashin Sashiko has reviewed this patch and found no issues. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261019011446.8344= 87-1-pasha.tatashin@soleen.com?part=3D8