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Subject[PATCH] mm/vmstat: don't do count if no needs
Date
For couple of vmstat account funcs, the caller usually doesn't check the
delta value, if delta == 0, irq or atomic operator is a waste. That's
better to be skipped.

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
---
mm/vmstat.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 3fb23a21f6dd..91f28146daa7 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -321,6 +321,9 @@ void __mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
long x;
long t;

+ if (!delta)
+ return;
+
x = delta + __this_cpu_read(*p);

t = __this_cpu_read(pcp->stat_threshold);
@@ -341,6 +344,9 @@ void __mod_node_page_state(struct pglist_data *pgdat, enum node_stat_item item,
long x;
long t;

+ if (!delta)
+ return;
+
x = delta + __this_cpu_read(*p);

t = __this_cpu_read(pcp->stat_threshold);
@@ -484,6 +490,9 @@ static inline void mod_zone_state(struct zone *zone,
s8 __percpu *p = pcp->vm_stat_diff + item;
long o, n, t, z;

+ if (!delta)
+ return;
+
do {
z = 0; /* overflow to zone counters */

@@ -518,6 +527,9 @@ static inline void mod_zone_state(struct zone *zone,
void mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
long delta)
{
+ if (!delta)
+ return;
+
mod_zone_state(zone, item, delta, 0);
}
EXPORT_SYMBOL(mod_zone_page_state);
@@ -541,6 +553,9 @@ static inline void mod_node_state(struct pglist_data *pgdat,
s8 __percpu *p = pcp->vm_node_stat_diff + item;
long o, n, t, z;

+ if (!delta)
+ return;
+
do {
z = 0; /* overflow to node counters */

@@ -581,6 +596,9 @@ EXPORT_SYMBOL(mod_node_page_state);

void inc_node_state(struct pglist_data *pgdat, enum node_stat_item item)
{
+ if (!delta)
+ return;
+
mod_node_state(pgdat, item, 1, 1);
}

@@ -604,6 +622,9 @@ void mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
{
unsigned long flags;

+ if (!delta)
+ return;
+
local_irq_save(flags);
__mod_zone_page_state(zone, item, delta);
local_irq_restore(flags);
@@ -647,6 +668,9 @@ void mod_node_page_state(struct pglist_data *pgdat, enum node_stat_item item,
{
unsigned long flags;

+ if (!delta)
+ return;
+
local_irq_save(flags);
__mod_node_page_state(pgdat, item, delta);
local_irq_restore(flags);
--
2.18.4
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