Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753925AbdLTDHb (ORCPT ); Tue, 19 Dec 2017 22:07:31 -0500 Received: from mga07.intel.com ([134.134.136.100]:28954 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751559AbdLTDHa (ORCPT ); Tue, 19 Dec 2017 22:07:30 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.45,429,1508828400"; d="scan'208";a="14097590" Subject: Re: [PATCH v2 2/5] mm: Extends local cpu counter vm_diff_nodestat from s8 to s16 To: Michal Hocko Cc: Greg Kroah-Hartman , Andrew Morton , Vlastimil Babka , Mel Gorman , Johannes Weiner , Christopher Lameter , YASUAKI ISHIMATSU , Andrey Ryabinin , Nikolay Borisov , Pavel Tatashin , David Rientjes , Sebastian Andrzej Siewior , Dave , Andi Kleen , Tim Chen , Jesper Dangaard Brouer , Ying Huang , Aaron Lu , Aubrey Li , Linux MM , Linux Kernel References: <1513665566-4465-1-git-send-email-kemi.wang@intel.com> <1513665566-4465-3-git-send-email-kemi.wang@intel.com> <20171219123829.GN2787@dhcp22.suse.cz> From: kemi Message-ID: Date: Wed, 20 Dec 2017 11:05:25 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 MIME-Version: 1.0 In-Reply-To: <20171219123829.GN2787@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3767 Lines: 104 On 2017年12月19日 20:38, Michal Hocko wrote: > On Tue 19-12-17 14:39:23, Kemi Wang wrote: >> The type s8 used for vm_diff_nodestat[] as local cpu counters has the >> limitation of global counters update frequency, especially for those >> monotone increasing type of counters like NUMA counters with more and more >> cpus/nodes. This patch extends the type of vm_diff_nodestat from s8 to s16 >> without any functionality change. >> >> before after >> sizeof(struct per_cpu_nodestat) 28 68 > > So it is 40B * num_cpus * num_nodes. Nothing really catastrophic IMHO > but the changelog is a bit silent about any numbers. This is a > performance optimization so it should better give us some. > This patch does not have any functionality change. So no performance gain I suppose. I guess you are talking about performance gain from the third patch which increases threshold size of NUMA counters. >> Signed-off-by: Kemi Wang >> --- >> include/linux/mmzone.h | 4 ++-- >> mm/vmstat.c | 16 ++++++++-------- >> 2 files changed, 10 insertions(+), 10 deletions(-) >> >> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h >> index c06d880..2da6b6f 100644 >> --- a/include/linux/mmzone.h >> +++ b/include/linux/mmzone.h >> @@ -289,8 +289,8 @@ struct per_cpu_pageset { >> }; >> >> struct per_cpu_nodestat { >> - s8 stat_threshold; >> - s8 vm_node_stat_diff[NR_VM_NODE_STAT_ITEMS]; >> + s16 stat_threshold; >> + s16 vm_node_stat_diff[NR_VM_NODE_STAT_ITEMS]; >> }; >> >> #endif /* !__GENERATING_BOUNDS.H */ >> diff --git a/mm/vmstat.c b/mm/vmstat.c >> index 1dd12ae..9c681cc 100644 >> --- a/mm/vmstat.c >> +++ b/mm/vmstat.c >> @@ -332,7 +332,7 @@ void __mod_node_page_state(struct pglist_data *pgdat, enum node_stat_item item, >> long delta) >> { >> struct per_cpu_nodestat __percpu *pcp = pgdat->per_cpu_nodestats; >> - s8 __percpu *p = pcp->vm_node_stat_diff + item; >> + s16 __percpu *p = pcp->vm_node_stat_diff + item; >> long x; >> long t; >> >> @@ -390,13 +390,13 @@ void __inc_zone_state(struct zone *zone, enum zone_stat_item item) >> void __inc_node_state(struct pglist_data *pgdat, enum node_stat_item item) >> { >> struct per_cpu_nodestat __percpu *pcp = pgdat->per_cpu_nodestats; >> - s8 __percpu *p = pcp->vm_node_stat_diff + item; >> - s8 v, t; >> + s16 __percpu *p = pcp->vm_node_stat_diff + item; >> + s16 v, t; >> >> v = __this_cpu_inc_return(*p); >> t = __this_cpu_read(pcp->stat_threshold); >> if (unlikely(v > t)) { >> - s8 overstep = t >> 1; >> + s16 overstep = t >> 1; >> >> node_page_state_add(v + overstep, pgdat, item); >> __this_cpu_write(*p, -overstep); >> @@ -434,13 +434,13 @@ void __dec_zone_state(struct zone *zone, enum zone_stat_item item) >> void __dec_node_state(struct pglist_data *pgdat, enum node_stat_item item) >> { >> struct per_cpu_nodestat __percpu *pcp = pgdat->per_cpu_nodestats; >> - s8 __percpu *p = pcp->vm_node_stat_diff + item; >> - s8 v, t; >> + s16 __percpu *p = pcp->vm_node_stat_diff + item; >> + s16 v, t; >> >> v = __this_cpu_dec_return(*p); >> t = __this_cpu_read(pcp->stat_threshold); >> if (unlikely(v < - t)) { >> - s8 overstep = t >> 1; >> + s16 overstep = t >> 1; >> >> node_page_state_add(v - overstep, pgdat, item); >> __this_cpu_write(*p, overstep); >> @@ -533,7 +533,7 @@ static inline void mod_node_state(struct pglist_data *pgdat, >> enum node_stat_item item, int delta, int overstep_mode) >> { >> struct per_cpu_nodestat __percpu *pcp = pgdat->per_cpu_nodestats; >> - s8 __percpu *p = pcp->vm_node_stat_diff + item; >> + s16 __percpu *p = pcp->vm_node_stat_diff + item; >> long o, n, t, z; >> >> do { >> -- >> 2.7.4 >> >