linux-kernel - [PATCH] xen: selfballoon: remove unnecessary static in frontswap

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Message-ID: <20170704183404.GA13813@embeddedgus>
Date:   Tue, 4 Jul 2017 13:34:05 -0500
From:   "Gustavo A. R. Silva" <garsilva@...eddedor.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>
Cc:     xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <garsilva@...eddedor.com>
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 <garsilva@...eddedor.com>
---
 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