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Commit 87af2ffd authored by Andreas Mohr's avatar Andreas Mohr Committed by Linus Torvalds
Browse files

[PATCH] i386 apm.c optimization 



- 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

Signed-off-by: default avatarAndreas Mohr <andi@lisas.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent a0b4da91

arch/i386/kernel/apm.c

+22 −17
Original line number Diff line number Diff line
@@ -374,14 +374,14 @@ static struct { 
	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 int bounce_interval = DEFAULT_BOUNCE_INTERVAL; 
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 @@ static int realmode_power_off = 1; 
#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_waitqueue); 
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 @@ static u8 apm_bios_call(u32 func, u32 ebx_in, u32 ecx_in, 
 *	@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 @@ static void apm_do_busy(void) 
#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_engage_power_management(u_short device, int enable) 
 

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 int queue_empty(struct apm_user *as) 


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 @@ static void queue_event(apm_event_t event, struct apm_user *sender) 
	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 void standby(void) 
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;