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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 45EEDC3524E for ; Wed, 19 Feb 2020 20:08:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0D7C124656 for ; Wed, 19 Feb 2020 20:08:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582142895; bh=K/D5JbPk2+EBYp2gmQA0q9ditYqXaZ6u/jNNJaQQNeU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=wL5yNyn/8S06rXwE0lekz9GtNmHJ1FqO3CBFNuofCk7hESRY7QS1dwajr8AIDZYau y5wXzQfNAkWt3t6gyy0Mbs9iMp9RuPZKhc4p2/bHSohVaz+iDaYwKL3RDfiMZfhjOZ cYKNJJqIlTkIs+SpIa7+CCqFvVG6N9NOXK3w2pw4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726875AbgBSUIN (ORCPT ); Wed, 19 Feb 2020 15:08:13 -0500 Received: from mail.kernel.org ([198.145.29.99]:46344 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726634AbgBSUIN (ORCPT ); Wed, 19 Feb 2020 15:08:13 -0500 Received: from X1 (nat-ab2241.sltdut.senawave.net [162.218.216.4]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 842F32176D; Wed, 19 Feb 2020 20:08:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582142891; bh=K/D5JbPk2+EBYp2gmQA0q9ditYqXaZ6u/jNNJaQQNeU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=U4t0+1H9+T91595fwF5FJlrfN5hAP7b2OvyDrCSy3zwLJrvS07mTsYuEM5DXHnFGp 4qFSz1jxRax7qvwJ19FfAf+jYHr05omtkY3xWKa9Bat7iEgGBVKKyg8tHE6D0KUotm JV5ctKrnTkl+82JgBHttCq5MEna+P72IO2uvUTbE= Date: Wed, 19 Feb 2020 12:08:10 -0800 From: Andrew Morton To: Wei Yang Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, rientjes@google.com, mhocko@kernel.org Subject: Re: [Patch v4] mm/vmscan.c: remove cpu online notification for now Message-Id: <20200219120810.c7677fa58594f5423549f59d@linux-foundation.org> In-Reply-To: <20200218224422.3407-1-richardw.yang@linux.intel.com> References: <20200218224422.3407-1-richardw.yang@linux.intel.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 19 Feb 2020 06:44:22 +0800 Wei Yang wrote: > kswapd kernel thread starts either with a CPU affinity set to the full > cpu mask of its target node or without any affinity at all if the node > is CPUless. There is a cpu hotplug callback (kswapd_cpu_online) that > implements an elaborate way to update this mask when a cpu is onlined. > > It is not really clear whether there is any actual benefit from this > scheme. Completely CPU-less NUMA nodes rarely gain a new CPU during > runtime. This is the case across all platforms, all architectures, all users for the next N years? I'm surprised that we know this with sufficient confidence. Can you explain how you came to make this assertion? > Drop the code for that reason. If there is a real usecase then > we can resurrect and simplify the code.