Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967227AbdLSMnV (ORCPT ); Tue, 19 Dec 2017 07:43:21 -0500 Received: from mx2.suse.de ([195.135.220.15]:35596 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965944AbdLSMnT (ORCPT ); Tue, 19 Dec 2017 07:43:19 -0500 Date: Tue, 19 Dec 2017 13:43:17 +0100 From: Michal Hocko To: Kemi Wang 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 Subject: Re: [PATCH v2 4/5] mm: use node_page_state_snapshot to avoid deviation Message-ID: <20171219124317.GP2787@dhcp22.suse.cz> References: <1513665566-4465-1-git-send-email-kemi.wang@intel.com> <1513665566-4465-5-git-send-email-kemi.wang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1513665566-4465-5-git-send-email-kemi.wang@intel.com> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3033 Lines: 78 On Tue 19-12-17 14:39:25, Kemi Wang wrote: > To avoid deviation, this patch uses node_page_state_snapshot instead of > node_page_state for node page stats query. > e.g. cat /proc/zoneinfo > cat /sys/devices/system/node/node*/vmstat > cat /sys/devices/system/node/node*/numastat > > As it is a slow path and would not be read frequently, I would worry about > it. The changelog doesn't explain why these counters needs any special treatment. _snapshot variants where used only for internal handling where the precision really mattered. We do not have any in-tree user and Jack has removed this by http://lkml.kernel.org/r/20171122094416.26019-1-jack@suse.cz which is already sitting in the mmotm tree. We can re-add it but that would really require a _very good_ reason. > Signed-off-by: Kemi Wang > --- > drivers/base/node.c | 17 ++++++++++------- > mm/vmstat.c | 2 +- > 2 files changed, 11 insertions(+), 8 deletions(-) > > diff --git a/drivers/base/node.c b/drivers/base/node.c > index a045ea1..cf303f8 100644 > --- a/drivers/base/node.c > +++ b/drivers/base/node.c > @@ -169,12 +169,15 @@ static ssize_t node_read_numastat(struct device *dev, > "interleave_hit %lu\n" > "local_node %lu\n" > "other_node %lu\n", > - node_page_state(NODE_DATA(dev->id), NUMA_HIT), > - node_page_state(NODE_DATA(dev->id), NUMA_MISS), > - node_page_state(NODE_DATA(dev->id), NUMA_FOREIGN), > - node_page_state(NODE_DATA(dev->id), NUMA_INTERLEAVE_HIT), > - node_page_state(NODE_DATA(dev->id), NUMA_LOCAL), > - node_page_state(NODE_DATA(dev->id), NUMA_OTHER)); > + node_page_state_snapshot(NODE_DATA(dev->id), NUMA_HIT), > + node_page_state_snapshot(NODE_DATA(dev->id), NUMA_MISS), > + node_page_state_snapshot(NODE_DATA(dev->id), > + NUMA_FOREIGN), > + node_page_state_snapshot(NODE_DATA(dev->id), > + NUMA_INTERLEAVE_HIT), > + node_page_state_snapshot(NODE_DATA(dev->id), NUMA_LOCAL), > + node_page_state_snapshot(NODE_DATA(dev->id), > + NUMA_OTHER)); > } > > static DEVICE_ATTR(numastat, S_IRUGO, node_read_numastat, NULL); > @@ -194,7 +197,7 @@ static ssize_t node_read_vmstat(struct device *dev, > for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) > n += sprintf(buf+n, "%s %lu\n", > vmstat_text[i + NR_VM_ZONE_STAT_ITEMS], > - node_page_state(pgdat, i)); > + node_page_state_snapshot(pgdat, i)); > > return n; > } > diff --git a/mm/vmstat.c b/mm/vmstat.c > index 64e08ae..d65f28d 100644 > --- a/mm/vmstat.c > +++ b/mm/vmstat.c > @@ -1466,7 +1466,7 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat, > for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) { > seq_printf(m, "\n %-12s %lu", > vmstat_text[i + NR_VM_ZONE_STAT_ITEMS], > - node_page_state(pgdat, i)); > + node_page_state_snapshot(pgdat, i)); > } > } > seq_printf(m, > -- > 2.7.4 > -- Michal Hocko SUSE Labs