2017-07-04 18:34:09

by Gustavo A. R. Silva

Subject: [PATCH] xen: selfballoon: remove unnecessary static in frontswap_selfshrink()

Remove unnecessary static on local variables last_frontswap_pages and
tgt_frontswap_pages. Such variables are initialized before being used,
on every execution path throughout the function. The statics have no
benefit and, removing them reduce the code size.

This issue was detected using Coccinelle and the following semantic patch:

@bad exists@
position p;
identifier x;
type T;
@@

static T x@p;
...
x = <+...x...+>

@@
identifier x;
expression e;
type T;
position p != bad.p;
@@

-static
T x@p;
... when != x
when strict
?x = e;

You can see a significant difference in the code size after executing
the size command, before and after the code change:

before:
text data bss dec hex filename
5633 3452 384 9469 24fd drivers/xen/xen-selfballoon.o

after:
text data bss dec hex filename
5576 3308 256 9140 23b4 drivers/xen/xen-selfballoon.o

Signed-off-by: Gustavo A. R. Silva <[email protected]>
---
drivers/xen/xen-selfballoon.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/xen/xen-selfballoon.c b/drivers/xen/xen-selfballoon.c
index 6662071..a67e955 100644
--- a/drivers/xen/xen-selfballoon.c
+++ b/drivers/xen/xen-selfballoon.c
@@ -151,8 +151,8 @@ static unsigned long frontswap_inertia_counter;
static void frontswap_selfshrink(void)
{
static unsigned long cur_frontswap_pages;
- static unsigned long last_frontswap_pages;
- static unsigned long tgt_frontswap_pages;
+ unsigned long last_frontswap_pages;
+ unsigned long tgt_frontswap_pages;

last_frontswap_pages = cur_frontswap_pages;
cur_frontswap_pages = frontswap_curr_pages();
--
2.5.0

2017-07-21 07:36:22

by Jürgen Groß

Subject: Re: [PATCH] xen: selfballoon: remove unnecessary static in frontswap_selfshrink()

On 04/07/17 20:34, Gustavo A. R. Silva wrote:
> Remove unnecessary static on local variables last_frontswap_pages and
> tgt_frontswap_pages. Such variables are initialized before being used,
> on every execution path throughout the function. The statics have no
> benefit and, removing them reduce the code size.
>
> This issue was detected using Coccinelle and the following semantic patch:
>
> @bad exists@
> position p;
> identifier x;
> type T;
> @@
>
> static T x@p;
> ...
> x = <+...x...+>
>
> @@
> identifier x;
> expression e;
> type T;
> position p != bad.p;
> @@
>
> -static
> T x@p;
> ... when != x
> when strict
> ?x = e;
>
> You can see a significant difference in the code size after executing
> the size command, before and after the code change:
>
> before:
> text data bss dec hex filename
> 5633 3452 384 9469 24fd drivers/xen/xen-selfballoon.o
>
> after:
> text data bss dec hex filename
> 5576 3308 256 9140 23b4 drivers/xen/xen-selfballoon.o
>
> Signed-off-by: Gustavo A. R. Silva <[email protected]>

Reviewed-by: Juergen Gross <[email protected]>


Sorry for late answer,

Juergen

2017-07-21 20:46:54

by Gustavo A. R. Silva

Subject: Re: [PATCH] xen: selfballoon: remove unnecessary static in frontswap_selfshrink()

Hi Juergen,

On 07/21/2017 02:36 AM, Juergen Gross wrote:
> On 04/07/17 20:34, Gustavo A. R. Silva wrote:
>> Remove unnecessary static on local variables last_frontswap_pages and
>> tgt_frontswap_pages. Such variables are initialized before being used,
>> on every execution path throughout the function. The statics have no
>> benefit and, removing them reduce the code size.
>>
>> This issue was detected using Coccinelle and the following semantic patch:
>>
>> @bad exists@
>> position p;
>> identifier x;
>> type T;
>> @@
>>
>> static T x@p;
>> ...
>> x = <+...x...+>
>>
>> @@
>> identifier x;
>> expression e;
>> type T;
>> position p != bad.p;
>> @@
>>
>> -static
>> T x@p;
>> ... when != x
>> when strict
>> ?x = e;
>>
>> You can see a significant difference in the code size after executing
>> the size command, before and after the code change:
>>
>> before:
>> text data bss dec hex filename
>> 5633 3452 384 9469 24fd drivers/xen/xen-selfballoon.o
>>
>> after:
>> text data bss dec hex filename
>> 5576 3308 256 9140 23b4 drivers/xen/xen-selfballoon.o
>>
>> Signed-off-by: Gustavo A. R. Silva <[email protected]>
>
> Reviewed-by: Juergen Gross <[email protected]>
>

Thank you!

--
Gustavo A. R. Silva

2017-07-28 09:34:39

by Jürgen Groß

Subject: Re: [PATCH] xen: selfballoon: remove unnecessary static in frontswap_selfshrink()

On 04/07/17 20:34, Gustavo A. R. Silva wrote:
> Remove unnecessary static on local variables last_frontswap_pages and
> tgt_frontswap_pages. Such variables are initialized before being used,
> on every execution path throughout the function. The statics have no
> benefit and, removing them reduce the code size.
>
> This issue was detected using Coccinelle and the following semantic patch:
>
> @bad exists@
> position p;
> identifier x;
> type T;
> @@
>
> static T x@p;
> ...
> x = <+...x...+>
>
> @@
> identifier x;
> expression e;
> type T;
> position p != bad.p;
> @@
>
> -static
> T x@p;
> ... when != x
> when strict
> ?x = e;
>
> You can see a significant difference in the code size after executing
> the size command, before and after the code change:
>
> before:
> text data bss dec hex filename
> 5633 3452 384 9469 24fd drivers/xen/xen-selfballoon.o
>
> after:
> text data bss dec hex filename
> 5576 3308 256 9140 23b4 drivers/xen/xen-selfballoon.o
>
> Signed-off-by: Gustavo A. R. Silva <[email protected]>

Committed to xen/tip.git for-linus-4.13b


Thanks,

Juergen