From: Andreas Mohr - 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: Andreas Mohr Signed-off-by: Andrew Morton --- arch/i386/kernel/apm.c | 39 ++++++++++++++++++++++----------------- 1 files changed, 22 insertions(+), 17 deletions(-) diff -puN arch/i386/kernel/apm.c~i386-apmc-optimization arch/i386/kernel/apm.c --- devel/arch/i386/kernel/apm.c~i386-apmc-optimization 2006-04-16 18:20:58.000000000 -0700 +++ devel-akpm/arch/i386/kernel/apm.c 2006-04-16 18:20:58.000000000 -0700 @@ -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_B 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_waitq 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 eb * @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 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 * 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 even 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; _