From: Michal Hocko <mhocko@kernel.org>
To: Kemi Wang <kemi.wang@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>,
Mel Gorman <mgorman@techsingularity.net>,
Johannes Weiner <hannes@cmpxchg.org>,
Christopher Lameter <cl@linux.com>,
YASUAKI ISHIMATSU <yasu.isimatu@gmail.com>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Nikolay Borisov <nborisov@suse.com>,
Pavel Tatashin <pasha.tatashin@oracle.com>,
David Rientjes <rientjes@google.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Dave <dave.hansen@linux.intel.com>,
Andi Kleen <andi.kleen@intel.com>,
Tim Chen <tim.c.chen@intel.com>,
Jesper Dangaard Brouer <brouer@redhat.com>,
Ying Huang <ying.huang@intel.com>, Aaron Lu <aaron.lu@intel.com>,
Aubrey Li <aubrey.li@intel.com>, Linux MM <linux-mm@kvack.org>,
Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 2/5] mm: Extends local cpu counter vm_diff_nodestat from s8 to s16
Date: Tue, 19 Dec 2017 13:38:29 +0100 [thread overview]
Message-ID: <20171219123829.GN2787@dhcp22.suse.cz> (raw)
In-Reply-To: <1513665566-4465-3-git-send-email-kemi.wang@intel.com>
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.
> Signed-off-by: Kemi Wang <kemi.wang@intel.com>
> ---
> 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
>
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2017-12-19 12:38 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-19 6:39 [PATCH v2 0/5] mm: NUMA stats code cleanup and enhancement Kemi Wang
2017-12-19 6:39 ` [PATCH v2 1/5] mm: migrate NUMA stats from per-zone to per-node Kemi Wang
2017-12-19 12:28 ` Michal Hocko
2017-12-20 5:32 ` kemi
2017-12-19 6:39 ` [PATCH v2 2/5] mm: Extends local cpu counter vm_diff_nodestat from s8 to s16 Kemi Wang
2017-12-19 12:38 ` Michal Hocko [this message]
2017-12-20 3:05 ` kemi
2017-12-19 16:05 ` Christopher Lameter
2017-12-19 16:20 ` Michal Hocko
2017-12-19 17:21 ` Christopher Lameter
2017-12-20 6:45 ` kemi
2017-12-19 6:39 ` [PATCH v2 3/5] mm: enlarge NUMA counters threshold size Kemi Wang
2017-12-19 12:40 ` Michal Hocko
2017-12-20 5:52 ` kemi
2017-12-20 10:12 ` Michal Hocko
2017-12-20 10:21 ` kemi
2017-12-21 8:06 ` kemi
2017-12-21 8:17 ` Michal Hocko
2017-12-21 8:23 ` kemi
2017-12-21 8:59 ` Michal Hocko
2017-12-21 10:31 ` kemi
2017-12-22 12:31 ` Michal Hocko
2017-12-21 17:10 ` Christopher Lameter
2017-12-22 2:06 ` kemi
2017-12-26 19:05 ` Christopher Lameter
2017-12-19 6:39 ` [PATCH v2 4/5] mm: use node_page_state_snapshot to avoid deviation Kemi Wang
2017-12-19 12:43 ` Michal Hocko
2017-12-20 6:07 ` kemi
2017-12-20 10:06 ` Michal Hocko
2017-12-20 10:24 ` kemi
2017-12-20 15:58 ` Christopher Lameter
2017-12-21 1:39 ` kemi
2017-12-19 6:39 ` [PATCH v2 5/5] mm: Rename zone_statistics() to numa_statistics() Kemi Wang
2017-12-19 12:44 ` Michal Hocko
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