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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham 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 6F6ADC32771 for ; Tue, 28 Jan 2020 00:39:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4B9D22467C for ; Tue, 28 Jan 2020 00:39:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726911AbgA1Ajb (ORCPT ); Mon, 27 Jan 2020 19:39:31 -0500 Received: from mga12.intel.com ([192.55.52.136]:7369 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726080AbgA1Ajb (ORCPT ); Mon, 27 Jan 2020 19:39:31 -0500 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 27 Jan 2020 16:39:30 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,371,1574150400"; d="scan'208";a="261265782" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by fmsmga002.fm.intel.com with ESMTP; 27 Jan 2020 16:39:29 -0800 Date: Tue, 28 Jan 2020 08:39:42 +0800 From: Wei Yang To: David Rientjes Cc: Wei Yang , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/vmscan.c: only adjust related kswapd cpu affinity when online cpu Message-ID: <20200128003942.GC20624@richard> Reply-To: Wei Yang References: <20200126132052.11921-1-richardw.yang@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jan 26, 2020 at 02:44:31PM -0800, David Rientjes wrote: >On Sun, 26 Jan 2020, Wei Yang wrote: > >> When onlining a cpu, kswapd_cpu_online() is called to adjust kswapd cpu >> affinity. >> >> Current routine does like this: >> >> * Iterate all the numa node >> * Adjust cpu affinity when node has an online cpu >> >> Actually we could improve this by: >> >> * Just adjust the numa node to which current online cpu belongs >> >> Because we know which numa node the cpu belongs to and this cpu would >> not affect other node. >> > >Is there ever a situation where the cpu to be onlined would have appeared >in the cpumask of another node and so a different kswapd's cpumask would >now include an off-node cpu? No, I don't think so. Per my understanding, kswapd_cpu_online() will be invoked when a cpu is onlined. And the particular cpu belongs to a particular numa node. So it is not necessary to iterate on every nodes. And current code use cpumask_and_any() to do the check. If my understanding is correct, the check would return true if this node has any online cpu. This is likely to be true. This is why I want to make the logic clear. > >> Signed-off-by: Wei Yang >> --- >> mm/vmscan.c | 19 ++++++++++--------- >> 1 file changed, 10 insertions(+), 9 deletions(-) >> >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index 572fb17c6273..19c92d35045c 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -4049,18 +4049,19 @@ unsigned long shrink_all_memory(unsigned long nr_to_reclaim) >> restore their cpu bindings. */ >> static int kswapd_cpu_online(unsigned int cpu) >> { >> - int nid; >> + int nid = cpu_to_node(cpu); >> + pg_data_t *pgdat; >> + const struct cpumask *mask; >> >> - for_each_node_state(nid, N_MEMORY) { >> - pg_data_t *pgdat = NODE_DATA(nid); >> - const struct cpumask *mask; >> + if (!node_state(nid, N_MEMORY)) >> + return 0; >> >> - mask = cpumask_of_node(pgdat->node_id); >> + pgdat = NODE_DATA(nid); >> + mask = cpumask_of_node(nid); >> + >> + /* One of our CPUs online: restore mask */ >> + set_cpus_allowed_ptr(pgdat->kswapd, mask); >> >> - if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) >> - /* One of our CPUs online: restore mask */ >> - set_cpus_allowed_ptr(pgdat->kswapd, mask); >> - } >> return 0; >> } >> >> -- >> 2.17.1 >> >> >> -- Wei Yang Help you, Help me