Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750988AbWCWDIw (ORCPT ); Wed, 22 Mar 2006 22:08:52 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751239AbWCWDIZ (ORCPT ); Wed, 22 Mar 2006 22:08:25 -0500 Received: from e35.co.us.ibm.com ([32.97.110.153]:15073 "EHLO e35.co.us.ibm.com") by vger.kernel.org with ESMTP id S932139AbWCWDGg (ORCPT ); Wed, 22 Mar 2006 22:06:36 -0500 Date: Wed, 22 Mar 2006 20:06:32 -0700 From: john stultz To: akpm@osdl.org Cc: john stultz , linux-kernel@vger.kernel.org, george@wildturkeyranch.net, Steven Rostedt , Thomas Gleixner , Ulrich Windl , Roman Zippel , Ingo Molnar , Paul Mackerras Message-Id: <20060323030631.19338.16925.sendpatchset@cog.beaverton.ibm.com> In-Reply-To: <20060323030547.19338.95102.sendpatchset@cog.beaverton.ibm.com> References: <20060323030547.19338.95102.sendpatchset@cog.beaverton.ibm.com> Subject: [PATCH 7/10] Time: i386 Conversion - part 2: Rework TSC Support Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 20955 Lines: 801 As part of the i386 conversion to the generic timekeeping infrastructure, this introduces a new tsc.c file. The code in this file replaces the TSC initialization, management and access code currently in timer_tsc.c (which will be removed) that we want to preserve. The code also introduces the following functionality: o tsc_khz: like cpu_khz but stores the TSC frequency on systems that do not change TSC frequency w/ CPU frequency o check/mark_tsc_unstable: accessor/modifier flag for TSC timekeeping usability o minor cleanups to calibration math. This patch also includes a one line __cpuinitdata fix from Zwane Mwaikambo. thanks -john Signed-off-by: John Stultz arch/i386/kernel/Makefile | 2 arch/i386/kernel/numaq.c | 10 arch/i386/kernel/setup.c | 1 arch/i386/kernel/timers/timer_tsc.c | 178 --------------- arch/i386/kernel/tsc.c | 316 ++++++++++++++++++++++++++++ drivers/acpi/processor_idle.c | 9 include/asm-i386/mach-default/mach_timer.h | 4 include/asm-i386/mach-summit/mach_mpparse.h | 3 include/asm-i386/timex.h | 34 --- include/asm-i386/tsc.h | 49 ++++ 10 files changed, 389 insertions(+), 217 deletions(-) linux-2.6.16_timeofday-arch-i386-part2_C1.patch ============================================ diff --git a/arch/i386/kernel/Makefile b/arch/i386/kernel/Makefile index 687a29b..16a2420 100644 --- a/arch/i386/kernel/Makefile +++ b/arch/i386/kernel/Makefile @@ -7,7 +7,7 @@ extra-y := head.o init_task.o vmlinux.ld obj-y := process.o semaphore.o signal.o entry.o traps.o irq.o \ ptrace.o time.o ioport.o ldt.o setup.o i8259.o sys_i386.o \ pci-dma.o i386_ksyms.o i387.o dmi_scan.o bootflag.o \ - quirks.o i8237.o i8253.o topology.o + quirks.o i8237.o i8253.o tsc.o topology.o obj-y += cpu/ obj-y += timers/ diff --git a/arch/i386/kernel/numaq.c b/arch/i386/kernel/numaq.c index 5f5b075..0caf146 100644 --- a/arch/i386/kernel/numaq.c +++ b/arch/i386/kernel/numaq.c @@ -79,10 +79,12 @@ int __init get_memcfg_numaq(void) return 1; } -static int __init numaq_dsc_disable(void) +static int __init numaq_tsc_disable(void) { - printk(KERN_DEBUG "NUMAQ: disabling TSC\n"); - tsc_disable = 1; + if (num_online_nodes() > 1) { + printk(KERN_DEBUG "NUMAQ: disabling TSC\n"); + tsc_disable = 1; + } return 0; } -core_initcall(numaq_dsc_disable); +arch_initcall(numaq_tsc_disable); diff --git a/arch/i386/kernel/setup.c b/arch/i386/kernel/setup.c index ab62a9f..1ac4963 100644 --- a/arch/i386/kernel/setup.c +++ b/arch/i386/kernel/setup.c @@ -1632,6 +1632,7 @@ void __init setup_arch(char **cmdline_p) conswitchp = &dummy_con; #endif #endif + tsc_init(); } #include "setup_arch_post.h" diff --git a/arch/i386/kernel/timers/timer_tsc.c b/arch/i386/kernel/timers/timer_tsc.c index 5e41ee2..243ec04 100644 --- a/arch/i386/kernel/timers/timer_tsc.c +++ b/arch/i386/kernel/timers/timer_tsc.c @@ -32,10 +32,6 @@ static unsigned long hpet_last; static struct timer_opts timer_tsc; #endif -static inline void cpufreq_delayed_get(void); - -int tsc_disable __devinitdata = 0; - static int use_tsc; /* Number of usecs that the last interrupt was delayed */ static int delay_at_last_interrupt; @@ -144,30 +140,6 @@ static unsigned long long monotonic_cloc return base + cycles_2_ns(this_offset - last_offset); } -/* - * Scheduler clock - returns current time in nanosec units. - */ -unsigned long long sched_clock(void) -{ - unsigned long long this_offset; - - /* - * In the NUMA case we dont use the TSC as they are not - * synchronized across all CPUs. - */ -#ifndef CONFIG_NUMA - if (!use_tsc) -#endif - /* no locking but a rare wrong value is not a big deal */ - return jiffies_64 * (1000000000 / HZ); - - /* Read the Time Stamp Counter */ - rdtscll(this_offset); - - /* return the value in ns */ - return cycles_2_ns(this_offset); -} - static void delay_tsc(unsigned long loops) { unsigned long bclock, now; @@ -231,136 +203,6 @@ static void mark_offset_tsc_hpet(void) } #endif - -#ifdef CONFIG_CPU_FREQ -#include - -static unsigned int cpufreq_delayed_issched = 0; -static unsigned int cpufreq_init = 0; -static struct work_struct cpufreq_delayed_get_work; - -static void handle_cpufreq_delayed_get(void *v) -{ - unsigned int cpu; - for_each_online_cpu(cpu) { - cpufreq_get(cpu); - } - cpufreq_delayed_issched = 0; -} - -/* if we notice lost ticks, schedule a call to cpufreq_get() as it tries - * to verify the CPU frequency the timing core thinks the CPU is running - * at is still correct. - */ -static inline void cpufreq_delayed_get(void) -{ - if (cpufreq_init && !cpufreq_delayed_issched) { - cpufreq_delayed_issched = 1; - printk(KERN_DEBUG "Losing some ticks... checking if CPU frequency changed.\n"); - schedule_work(&cpufreq_delayed_get_work); - } -} - -/* If the CPU frequency is scaled, TSC-based delays will need a different - * loops_per_jiffy value to function properly. - */ - -static unsigned int ref_freq = 0; -static unsigned long loops_per_jiffy_ref = 0; - -#ifndef CONFIG_SMP -static unsigned long fast_gettimeoffset_ref = 0; -static unsigned int cpu_khz_ref = 0; -#endif - -static int -time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, - void *data) -{ - struct cpufreq_freqs *freq = data; - - if (val != CPUFREQ_RESUMECHANGE) - write_seqlock_irq(&xtime_lock); - if (!ref_freq) { - if (!freq->old){ - ref_freq = freq->new; - goto end; - } - ref_freq = freq->old; - loops_per_jiffy_ref = cpu_data[freq->cpu].loops_per_jiffy; -#ifndef CONFIG_SMP - fast_gettimeoffset_ref = fast_gettimeoffset_quotient; - cpu_khz_ref = cpu_khz; -#endif - } - - if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) || - (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) || - (val == CPUFREQ_RESUMECHANGE)) { - if (!(freq->flags & CPUFREQ_CONST_LOOPS)) - cpu_data[freq->cpu].loops_per_jiffy = cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new); -#ifndef CONFIG_SMP - if (cpu_khz) - cpu_khz = cpufreq_scale(cpu_khz_ref, ref_freq, freq->new); - if (use_tsc) { - if (!(freq->flags & CPUFREQ_CONST_LOOPS)) { - fast_gettimeoffset_quotient = cpufreq_scale(fast_gettimeoffset_ref, freq->new, ref_freq); - set_cyc2ns_scale(cpu_khz); - } - } -#endif - } - -end: - if (val != CPUFREQ_RESUMECHANGE) - write_sequnlock_irq(&xtime_lock); - - return 0; -} - -static struct notifier_block time_cpufreq_notifier_block = { - .notifier_call = time_cpufreq_notifier -}; - - -static int __init cpufreq_tsc(void) -{ - int ret; - INIT_WORK(&cpufreq_delayed_get_work, handle_cpufreq_delayed_get, NULL); - ret = cpufreq_register_notifier(&time_cpufreq_notifier_block, - CPUFREQ_TRANSITION_NOTIFIER); - if (!ret) - cpufreq_init = 1; - return ret; -} -core_initcall(cpufreq_tsc); - -#else /* CONFIG_CPU_FREQ */ -static inline void cpufreq_delayed_get(void) { return; } -#endif - -int recalibrate_cpu_khz(void) -{ -#ifndef CONFIG_SMP - unsigned int cpu_khz_old = cpu_khz; - - if (cpu_has_tsc) { - local_irq_disable(); - init_cpu_khz(); - local_irq_enable(); - cpu_data[0].loops_per_jiffy = - cpufreq_scale(cpu_data[0].loops_per_jiffy, - cpu_khz_old, - cpu_khz); - return 0; - } else - return -ENODEV; -#else - return -ENODEV; -#endif -} -EXPORT_SYMBOL(recalibrate_cpu_khz); - static void mark_offset_tsc(void) { unsigned long lost,delay; @@ -451,9 +293,6 @@ static void mark_offset_tsc(void) clock_fallback(); } - /* ... but give the TSC a fair chance */ - if (lost_count > 25) - cpufreq_delayed_get(); } else lost_count = 0; /* update the monotonic base value */ @@ -578,23 +417,6 @@ static int tsc_resume(void) return 0; } -#ifndef CONFIG_X86_TSC -/* disable flag for tsc. Takes effect by clearing the TSC cpu flag - * in cpu/common.c */ -static int __init tsc_setup(char *str) -{ - tsc_disable = 1; - return 1; -} -#else -static int __init tsc_setup(char *str) -{ - printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, " - "cannot disable TSC.\n"); - return 1; -} -#endif -__setup("notsc", tsc_setup); diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c new file mode 100644 index 0000000..b1f588c --- /dev/null +++ b/arch/i386/kernel/tsc.c @@ -0,0 +1,316 @@ +/* + * This code largely moved from arch/i386/kernel/timer/timer_tsc.c + * which was originally moved from arch/i386/kernel/time.c. + * See comments there for proper credits. + */ + +#include +#include +#include +#include + +#include +#include + +#include "mach_timer.h" + +/* + * On some systems the TSC frequency does not + * change with the cpu frequency. So we need + * an extra value to store the TSC freq + */ +unsigned int tsc_khz; + +int tsc_disable __cpuinitdata = 0; + +#ifdef CONFIG_X86_TSC +static int __init tsc_setup(char *str) +{ + printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, " + "cannot disable TSC.\n"); + return 1; +} +#else +/* + * disable flag for tsc. Takes effect by clearing the TSC cpu flag + * in cpu/common.c + */ +static int __init tsc_setup(char *str) +{ + tsc_disable = 1; + + return 1; +} +#endif + +__setup("notsc", tsc_setup); + + +/* + * code to mark and check if the TSC is unstable + * due to cpufreq or due to unsynced TSCs + */ +static int tsc_unstable; + +static inline int check_tsc_unstable(void) +{ + return tsc_unstable; +} + +void mark_tsc_unstable(void) +{ + tsc_unstable = 1; +} +EXPORT_SYMBOL_GPL(mark_tsc_unstable); + +/* Accellerators for sched_clock() + * convert from cycles(64bits) => nanoseconds (64bits) + * basic equation: + * ns = cycles / (freq / ns_per_sec) + * ns = cycles * (ns_per_sec / freq) + * ns = cycles * (10^9 / (cpu_khz * 10^3)) + * ns = cycles * (10^6 / cpu_khz) + * + * Then we use scaling math (suggested by george@mvista.com) to get: + * ns = cycles * (10^6 * SC / cpu_khz) / SC + * ns = cycles * cyc2ns_scale / SC + * + * And since SC is a constant power of two, we can convert the div + * into a shift. + * + * We can use khz divisor instead of mhz to keep a better percision, since + * cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits. + * (mathieu.desnoyers@polymtl.ca) + * + * -johnstul@us.ibm.com "math is hard, lets go shopping!" + */ +static unsigned long cyc2ns_scale __read_mostly; + +#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */ + +static inline void set_cyc2ns_scale(unsigned long cpu_khz) +{ + cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR)/cpu_khz; +} + +static inline unsigned long long cycles_2_ns(unsigned long long cyc) +{ + return (cyc * cyc2ns_scale) >> CYC2NS_SCALE_FACTOR; +} + +/* + * Scheduler clock - returns current time in nanosec units. + */ +unsigned long long sched_clock(void) +{ + unsigned long long this_offset; + + /* + * in the NUMA case we dont use the TSC as they are not + * synchronized across all CPUs. + */ +#ifndef CONFIG_NUMA + if (!cpu_khz || check_tsc_unstable()) +#endif + /* no locking but a rare wrong value is not a big deal */ + return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ); + + /* read the Time Stamp Counter: */ + rdtscll(this_offset); + + /* return the value in ns */ + return cycles_2_ns(this_offset); +} + +static unsigned long calculate_cpu_khz(void) +{ + unsigned long long start, end; + unsigned long count; + u64 delta64; + int i; + unsigned long flags; + + local_irq_save(flags); + + /* run 3 times to ensure the cache is warm */ + for (i = 0; i < 3; i++) { + mach_prepare_counter(); + rdtscll(start); + mach_countup(&count); + rdtscll(end); + } + /* + * Error: ECTCNEVERSET + * The CTC wasn't reliable: we got a hit on the very first read, + * or the CPU was so fast/slow that the quotient wouldn't fit in + * 32 bits.. + */ + if (count <= 1) + goto err; + + delta64 = end - start; + + /* cpu freq too fast: */ + if (delta64 > (1ULL<<32)) + goto err; + + /* cpu freq too slow: */ + if (delta64 <= CALIBRATE_TIME_MSEC) + goto err; + + delta64 += CALIBRATE_TIME_MSEC/2; /* round for do_div */ + do_div(delta64,CALIBRATE_TIME_MSEC); + + local_irq_restore(flags); + return (unsigned long)delta64; +err: + local_irq_restore(flags); + return 0; +} + +int recalibrate_cpu_khz(void) +{ +#ifndef CONFIG_SMP + unsigned long cpu_khz_old = cpu_khz; + + if (cpu_has_tsc) { + cpu_khz = calculate_cpu_khz(); + tsc_khz = cpu_khz; + cpu_data[0].loops_per_jiffy = + cpufreq_scale(cpu_data[0].loops_per_jiffy, + cpu_khz_old, cpu_khz); + return 0; + } else + return -ENODEV; +#else + return -ENODEV; +#endif +} + +EXPORT_SYMBOL(recalibrate_cpu_khz); + +void tsc_init(void) +{ + if (!cpu_has_tsc || tsc_disable) + return; + + cpu_khz = calculate_cpu_khz(); + tsc_khz = cpu_khz; + + if (!cpu_khz) + return; + + printk("Detected %lu.%03lu MHz processor.\n", + (unsigned long)cpu_khz / 1000, + (unsigned long)cpu_khz % 1000); + + set_cyc2ns_scale(cpu_khz); +} + +#ifdef CONFIG_CPU_FREQ + +static unsigned int cpufreq_delayed_issched = 0; +static unsigned int cpufreq_init = 0; +static struct work_struct cpufreq_delayed_get_work; + +static void handle_cpufreq_delayed_get(void *v) +{ + unsigned int cpu; + + for_each_online_cpu(cpu) + cpufreq_get(cpu); + + cpufreq_delayed_issched = 0; +} + +/* + * if we notice cpufreq oddness, schedule a call to cpufreq_get() as it tries + * to verify the CPU frequency the timing core thinks the CPU is running + * at is still correct. + */ +static inline void cpufreq_delayed_get(void) +{ + if (cpufreq_init && !cpufreq_delayed_issched) { + cpufreq_delayed_issched = 1; + printk(KERN_DEBUG "Checking if CPU frequency changed.\n"); + schedule_work(&cpufreq_delayed_get_work); + } +} + +/* + * if the CPU frequency is scaled, TSC-based delays will need a different + * loops_per_jiffy value to function properly. + */ +static unsigned int ref_freq = 0; +static unsigned long loops_per_jiffy_ref = 0; +static unsigned long cpu_khz_ref = 0; + +static int +time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, void *data) +{ + struct cpufreq_freqs *freq = data; + + if (val != CPUFREQ_RESUMECHANGE) + write_seqlock_irq(&xtime_lock); + + if (!ref_freq) { + if (!freq->old){ + ref_freq = freq->new; + goto end; + } + ref_freq = freq->old; + loops_per_jiffy_ref = cpu_data[freq->cpu].loops_per_jiffy; + cpu_khz_ref = cpu_khz; + } + + if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) || + (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) || + (val == CPUFREQ_RESUMECHANGE)) { + if (!(freq->flags & CPUFREQ_CONST_LOOPS)) + cpu_data[freq->cpu].loops_per_jiffy = + cpufreq_scale(loops_per_jiffy_ref, + ref_freq, freq->new); + + if (cpu_khz) { + + if (num_online_cpus() == 1) + cpu_khz = cpufreq_scale(cpu_khz_ref, + ref_freq, freq->new); + if (!(freq->flags & CPUFREQ_CONST_LOOPS)) { + tsc_khz = cpu_khz; + set_cyc2ns_scale(cpu_khz); + /* + * TSC based sched_clock turns + * to junk w/ cpufreq + */ + mark_tsc_unstable(); + } + } + } +end: + if (val != CPUFREQ_RESUMECHANGE) + write_sequnlock_irq(&xtime_lock); + + return 0; +} + +static struct notifier_block time_cpufreq_notifier_block = { + .notifier_call = time_cpufreq_notifier +}; + +static int __init cpufreq_tsc(void) +{ + int ret; + + INIT_WORK(&cpufreq_delayed_get_work, handle_cpufreq_delayed_get, NULL); + ret = cpufreq_register_notifier(&time_cpufreq_notifier_block, + CPUFREQ_TRANSITION_NOTIFIER); + if (!ret) + cpufreq_init = 1; + + return ret; +} + +core_initcall(cpufreq_tsc); + +#endif diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index eb730a8..9a54eba 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -369,6 +369,11 @@ static void acpi_processor_idle(void) t2 = inl(acpi_fadt.xpm_tmr_blk.address); /* Get end time (ticks) */ t2 = inl(acpi_fadt.xpm_tmr_blk.address); + +#ifdef CONFIG_GENERIC_TIME + /* TSC halts in C2, so notify users */ + mark_tsc_unstable(); +#endif /* Re-enable interrupts */ local_irq_enable(); set_thread_flag(TIF_POLLING_NRFLAG); @@ -409,6 +414,10 @@ static void acpi_processor_idle(void) ACPI_MTX_DO_NOT_LOCK); } +#ifdef CONFIG_GENERIC_TIME + /* TSC halts in C3, so notify users */ + mark_tsc_unstable(); +#endif /* Re-enable interrupts */ local_irq_enable(); set_thread_flag(TIF_POLLING_NRFLAG); diff --git a/include/asm-i386/mach-default/mach_timer.h b/include/asm-i386/mach-default/mach_timer.h index 4b9703b..807992f 100644 --- a/include/asm-i386/mach-default/mach_timer.h +++ b/include/asm-i386/mach-default/mach_timer.h @@ -15,7 +15,9 @@ #ifndef _MACH_TIMER_H #define _MACH_TIMER_H -#define CALIBRATE_LATCH (5 * LATCH) +#define CALIBRATE_TIME_MSEC 30 /* 30 msecs */ +#define CALIBRATE_LATCH \ + ((CLOCK_TICK_RATE * CALIBRATE_TIME_MSEC + 1000/2)/1000) static inline void mach_prepare_counter(void) { diff --git a/include/asm-i386/mach-summit/mach_mpparse.h b/include/asm-i386/mach-summit/mach_mpparse.h index 1cce2b9..9426839 100644 --- a/include/asm-i386/mach-summit/mach_mpparse.h +++ b/include/asm-i386/mach-summit/mach_mpparse.h @@ -2,6 +2,7 @@ #define __ASM_MACH_MPPARSE_H #include +#include extern int use_cyclone; @@ -29,6 +30,7 @@ static inline int mps_oem_check(struct m (!strncmp(productid, "VIGIL SMP", 9) || !strncmp(productid, "EXA", 3) || !strncmp(productid, "RUTHLESS SMP", 12))){ + mark_tsc_unstable(); use_cyclone = 1; /*enable cyclone-timer*/ setup_summit(); return 1; @@ -42,6 +44,7 @@ static inline int acpi_madt_oem_check(ch if (!strncmp(oem_id, "IBM", 3) && (!strncmp(oem_table_id, "SERVIGIL", 8) || !strncmp(oem_table_id, "EXA", 3))){ + mark_tsc_unstable(); use_cyclone = 1; /*enable cyclone-timer*/ setup_summit(); return 1; diff --git a/include/asm-i386/timex.h b/include/asm-i386/timex.h index 292b5a6..ebcc74e 100644 --- a/include/asm-i386/timex.h +++ b/include/asm-i386/timex.h @@ -8,6 +8,7 @@ #include #include +#include #ifdef CONFIG_X86_ELAN # define CLOCK_TICK_RATE 1189200 /* AMD Elan has different frequency! */ @@ -16,39 +17,6 @@ #endif -/* - * Standard way to access the cycle counter on i586+ CPUs. - * Currently only used on SMP. - * - * If you really have a SMP machine with i486 chips or older, - * compile for that, and this will just always return zero. - * That's ok, it just means that the nicer scheduling heuristics - * won't work for you. - * - * We only use the low 32 bits, and we'd simply better make sure - * that we reschedule before that wraps. Scheduling at least every - * four billion cycles just basically sounds like a good idea, - * regardless of how fast the machine is. - */ -typedef unsigned long long cycles_t; - -static inline cycles_t get_cycles (void) -{ - unsigned long long ret=0; - -#ifndef CONFIG_X86_TSC - if (!cpu_has_tsc) - return 0; -#endif - -#if defined(CONFIG_X86_GENERIC) || defined(CONFIG_X86_TSC) - rdtscll(ret); -#endif - return ret; -} - -extern unsigned int cpu_khz; - extern int read_current_timer(unsigned long *timer_value); #define ARCH_HAS_READ_CURRENT_TIMER 1 diff --git a/include/asm-i386/tsc.h b/include/asm-i386/tsc.h new file mode 100644 index 0000000..97b828c --- /dev/null +++ b/include/asm-i386/tsc.h @@ -0,0 +1,49 @@ +/* + * linux/include/asm-i386/tsc.h + * + * i386 TSC related functions + */ +#ifndef _ASM_i386_TSC_H +#define _ASM_i386_TSC_H + +#include +#include + +/* + * Standard way to access the cycle counter on i586+ CPUs. + * Currently only used on SMP. + * + * If you really have a SMP machine with i486 chips or older, + * compile for that, and this will just always return zero. + * That's ok, it just means that the nicer scheduling heuristics + * won't work for you. + * + * We only use the low 32 bits, and we'd simply better make sure + * that we reschedule before that wraps. Scheduling at least every + * four billion cycles just basically sounds like a good idea, + * regardless of how fast the machine is. + */ +typedef unsigned long long cycles_t; + +extern unsigned int cpu_khz; +extern unsigned int tsc_khz; + +static inline cycles_t get_cycles(void) +{ + unsigned long long ret = 0; + +#ifndef CONFIG_X86_TSC + if (!cpu_has_tsc) + return 0; +#endif + +#if defined(CONFIG_X86_GENERIC) || defined(CONFIG_X86_TSC) + rdtscll(ret); +#endif + return ret; +} + +extern void tsc_init(void); +extern void mark_tsc_unstable(void); + +#endif - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/