From: Andreas Mohr <andi@rhlx01.fht-esslingen.de>
To: Andrew Morton <akpm@osdl.org>
Cc: sfr@canb.auug.org.au, linux-laptop@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: [PATCH] -mm: i386 apm.c optimization
Date: Mon, 17 Apr 2006 00:05:53 +0200 [thread overview]
Message-ID: <20060416220552.GA22998@rhlx01.fht-esslingen.de> (raw)
Hello all,
- avoid expensive modulo (integer division) which happened
since APM_MAX_EVENTS is 20 (non-power-of-2)
- kill compiler warnings by initializing two variables
- add __read_mostly to some important static variables that are read often
(by idle loop etc.)
- constify several structures
Patch tested on 2.6.16-ck5, rediffed against 2.6.17-rc1-mm2.
Signed-off-by: Andreas Mohr <andi@lisas.de>
diff -urN linux-2.6.17-rc1-mm2.orig/arch/i386/kernel/apm.c linux-2.6.17-rc1-mm2/arch/i386/kernel/apm.c
--- linux-2.6.17-rc1-mm2.orig/arch/i386/kernel/apm.c 2006-04-03 05:22:10.000000000 +0200
+++ linux-2.6.17-rc1-mm2/arch/i386/kernel/apm.c 2006-04-16 23:49:00.000000000 +0200
@@ -374,14 +374,14 @@
unsigned short segment;
} apm_bios_entry;
static int clock_slowed;
-static int idle_threshold = DEFAULT_IDLE_THRESHOLD;
-static int idle_period = DEFAULT_IDLE_PERIOD;
+static int idle_threshold __read_mostly = DEFAULT_IDLE_THRESHOLD;
+static int idle_period __read_mostly = DEFAULT_IDLE_PERIOD;
static int set_pm_idle;
static int suspends_pending;
static int standbys_pending;
static int ignore_sys_suspend;
static int ignore_normal_resume;
-static int bounce_interval = DEFAULT_BOUNCE_INTERVAL;
+static int bounce_interval __read_mostly = DEFAULT_BOUNCE_INTERVAL;
#ifdef CONFIG_APM_RTC_IS_GMT
# define clock_cmos_diff 0
@@ -390,8 +390,8 @@
static long clock_cmos_diff;
static int got_clock_diff;
#endif
-static int debug;
-static int smp;
+static int debug __read_mostly;
+static int smp __read_mostly;
static int apm_disabled = -1;
#ifdef CONFIG_SMP
static int power_off;
@@ -403,8 +403,8 @@
#else
static int realmode_power_off;
#endif
-static int exit_kapmd;
-static int kapmd_running;
+static int exit_kapmd __read_mostly;
+static int kapmd_running __read_mostly;
#ifdef CONFIG_APM_ALLOW_INTS
static int allow_ints = 1;
#else
@@ -416,15 +416,15 @@
static DECLARE_WAIT_QUEUE_HEAD(apm_suspend_waitqueue);
static struct apm_user * user_list;
static DEFINE_SPINLOCK(user_list_lock);
-static struct desc_struct bad_bios_desc = { 0, 0x00409200 };
+static const struct desc_struct bad_bios_desc = { 0, 0x00409200 };
-static char driver_version[] = "1.16ac"; /* no spaces */
+static const char driver_version[] = "1.16ac"; /* no spaces */
/*
* APM event names taken from the APM 1.2 specification. These are
* the message codes that the BIOS uses to tell us about events
*/
-static char * apm_event_name[] = {
+static const char * const apm_event_name[] = {
"system standby",
"system suspend",
"normal resume",
@@ -616,7 +616,7 @@
* @ecx_in: ECX register value for BIOS call
* @eax: EAX register on return from the BIOS call
*
- * Make a BIOS call that does only returns one value, or just status.
+ * Make a BIOS call that returns one value only, or just status.
* If there is an error, then the error code is returned in AH
* (bits 8-15 of eax) and this function returns non-zero. This is
* used for simpler BIOS operations. This call may hold interrupts
@@ -822,7 +822,7 @@
#define IDLE_CALC_LIMIT (HZ * 100)
#define IDLE_LEAKY_MAX 16
-static void (*original_pm_idle)(void);
+static void (*original_pm_idle)(void) __read_mostly;
/**
* apm_cpu_idle - cpu idling for APM capable Linux
@@ -1063,7 +1063,8 @@
static int apm_console_blank(int blank)
{
- int error, i;
+ int error = APM_NOT_ENGAGED; /* silence gcc */
+ int i;
u_short state;
static const u_short dev[3] = { 0x100, 0x1FF, 0x101 };
@@ -1104,7 +1105,8 @@
static apm_event_t get_queued_event(struct apm_user *as)
{
- as->event_tail = (as->event_tail + 1) % APM_MAX_EVENTS;
+ if (++as->event_tail >= APM_MAX_EVENTS)
+ as->event_tail = 0;
return as->events[as->event_tail];
}
@@ -1118,13 +1120,16 @@
for (as = user_list; as != NULL; as = as->next) {
if ((as == sender) || (!as->reader))
continue;
- as->event_head = (as->event_head + 1) % APM_MAX_EVENTS;
+ if (++as->event_head >= APM_MAX_EVENTS)
+ as->event_head = 0;
+
if (as->event_head == as->event_tail) {
static int notified;
if (notified++ == 0)
printk(KERN_ERR "apm: an event queue overflowed\n");
- as->event_tail = (as->event_tail + 1) % APM_MAX_EVENTS;
+ if (++as->event_tail >= APM_MAX_EVENTS)
+ as->event_tail = 0;
}
as->events[as->event_head] = event;
if ((!as->suser) || (!as->writer))
@@ -1282,7 +1287,7 @@
static apm_event_t get_event(void)
{
int error;
- apm_event_t event;
+ apm_event_t event = APM_NO_EVENTS; /* silence gcc */
apm_eventinfo_t info;
static int notified;
next reply other threads:[~2006-04-16 22:05 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-04-16 22:05 Andreas Mohr [this message]
2006-05-05 13:55 ` [PATCH] -mm: i386 apm.c optimization Bill Davidsen
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