* [PATCH] mm/vmstat: don't do count if no needs
@ 2020-07-20 5:23 Alex Shi
2020-07-20 5:42 ` Alex Shi
0 siblings, 1 reply; 4+ messages in thread
From: Alex Shi @ 2020-07-20 5:23 UTC (permalink / raw)
Cc: Alex Shi, Andrew Morton, linux-mm, linux-kernel
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
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] mm/vmstat: don't do count if no needs
2020-07-20 5:23 [PATCH] mm/vmstat: don't do count if no needs Alex Shi
@ 2020-07-20 5:42 ` Alex Shi
2020-07-20 23:14 ` Andrew Morton
0 siblings, 1 reply; 4+ messages in thread
From: Alex Shi @ 2020-07-20 5:42 UTC (permalink / raw)
Cc: Andrew Morton, linux-mm, linux-kernel
From 4cb977d34227e4bafa95b8da5e47dbd8b6141d26 Mon Sep 17 00:00:00 2001
From: Alex Shi <alex.shi@linux.alibaba.com>
Date: Mon, 20 Jul 2020 11:50:12 +0800
Subject: [PATCH v2] mm/vmstat: don't do count if no needs
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, also add unlikey() since !delta is less happened.
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 | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 3fb23a21f6dd..b02d99dff443 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 (unlikely(!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 (unlikely(!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 (unlikely(!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 (unlikely(!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 (unlikely(!delta))
+ return;
+
do {
z = 0; /* overflow to node counters */
@@ -604,6 +619,9 @@ void mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
{
unsigned long flags;
+ if (unlikely(!delta))
+ return;
+
local_irq_save(flags);
__mod_zone_page_state(zone, item, delta);
local_irq_restore(flags);
@@ -647,6 +665,9 @@ void mod_node_page_state(struct pglist_data *pgdat, enum node_stat_item item,
{
unsigned long flags;
+ if (unlikely(!delta))
+ return;
+
local_irq_save(flags);
__mod_node_page_state(pgdat, item, delta);
local_irq_restore(flags);
--
2.18.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] mm/vmstat: don't do count if no needs
2020-07-20 5:42 ` Alex Shi
@ 2020-07-20 23:14 ` Andrew Morton
2020-07-21 3:07 ` Alex Shi
0 siblings, 1 reply; 4+ messages in thread
From: Andrew Morton @ 2020-07-20 23:14 UTC (permalink / raw)
To: Alex Shi; +Cc: linux-mm, linux-kernel
On Mon, 20 Jul 2020 13:42:45 +0800 Alex Shi <alex.shi@linux.alibaba.com> wrote:
>
> 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, also add unlikey() since !delta is less happened.
>
> ...
>
> --- 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 (unlikely(!delta))
> + return;
> +
Do we know that delta==0 is frequent enough to make the change a net
benefit?
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] mm/vmstat: don't do count if no needs
2020-07-20 23:14 ` Andrew Morton
@ 2020-07-21 3:07 ` Alex Shi
0 siblings, 0 replies; 4+ messages in thread
From: Alex Shi @ 2020-07-21 3:07 UTC (permalink / raw)
To: Andrew Morton; +Cc: linux-mm, linux-kernel
在 2020/7/21 上午7:14, Andrew Morton 写道:
>> --- 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 (unlikely(!delta))
>> + return;
>> +
> Do we know that delta==0 is frequent enough to make the change a net
> benefit?
Uh,I check again. it seems no much place delta==0, forget this patch.
Thanks
Alex
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2020-07-21 3:07 UTC | newest]
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2020-07-20 5:23 [PATCH] mm/vmstat: don't do count if no needs Alex Shi
2020-07-20 5:42 ` Alex Shi
2020-07-20 23:14 ` Andrew Morton
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