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x86: merge sched_clock handling

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Move the basic global variable definitions and sched_clock handling in the
common "tsc.c" file.

 - Unify notsc kernel command line handling for 32 bit and 64bit.
 - Functional changes for 64bit.
        - "tsc_disabled" is updated if "notsc" is passed at boottime.
        - Fallback to jiffies for sched_clock, incase notsc is passed on
	  commandline.

Signed-off-by: Alok N Kataria <akataria@vmware.com>
Signed-off-by: Dan Hecht <dhecht@vmware.com>
Cc: Dan Hecht <dhecht@vmware.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Alok Kataria 2008-07-01 11:43:18 -07:00 committed by Ingo Molnar
parent 746f2eb790
commit 0ef9553332
5 changed files with 100 additions and 144 deletions
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2
arch/x86/kernel/Makefile
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@ -26,7 +26,7 @@ obj-$(CONFIG_X86_64) += syscall_64.o vsyscall_64.o
obj-y += bootflag.o e820.o
obj-y += pci-dma.o quirks.o i8237.o topology.o kdebugfs.o
obj-y += alternative.o i8253.o pci-nommu.o
obj-y += tsc_$(BITS).o io_delay.o rtc.o
obj-y += tsc_$(BITS).o io_delay.o rtc.o tsc.o
obj-$(CONFIG_X86_TRAMPOLINE) += trampoline.o
obj-y += process.o

3
arch/x86/kernel/time_32.c
View File

@ -39,9 +39,6 @@
#include "do_timer.h"
unsigned int cpu_khz; /* Detected as we calibrate the TSC */
EXPORT_SYMBOL(cpu_khz);
int timer_ack;
unsigned long profile_pc(struct pt_regs *regs)

86
arch/x86/kernel/tsc.c Normal file
View File

@ -0,0 +1,86 @@
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/timer.h>
unsigned int cpu_khz; /* TSC clocks / usec, not used here */
EXPORT_SYMBOL(cpu_khz);
unsigned int tsc_khz;
EXPORT_SYMBOL(tsc_khz);
/*
* TSC can be unstable due to cpufreq or due to unsynced TSCs
*/
int tsc_unstable;
/* native_sched_clock() is called before tsc_init(), so
we must start with the TSC soft disabled to prevent
erroneous rdtsc usage on !cpu_has_tsc processors */
int tsc_disabled = -1;
/*
* Scheduler clock - returns current time in nanosec units.
*/
u64 native_sched_clock(void)
{
u64 this_offset;
/*
* Fall back to jiffies if there's no TSC available:
* ( But note that we still use it if the TSC is marked
* unstable. We do this because unlike Time Of Day,
* the scheduler clock tolerates small errors and it's
* very important for it to be as fast as the platform
* can achive it. )
*/
if (unlikely(tsc_disabled)) {
/* 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);
}
/* We need to define a real function for sched_clock, to override the
weak default version */
#ifdef CONFIG_PARAVIRT
unsigned long long sched_clock(void)
{
return paravirt_sched_clock();
}
#else
unsigned long long
sched_clock(void) __attribute__((alias("native_sched_clock")));
#endif
int check_tsc_unstable(void)
{
return tsc_unstable;
}
EXPORT_SYMBOL_GPL(check_tsc_unstable);
#ifdef CONFIG_X86_TSC
int __init notsc_setup(char *str)
{
printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, "
"cannot disable TSC completely.\n");
tsc_disabled = 1;
return 1;
}
#else
/*
* disable flag for tsc. Takes effect by clearing the TSC cpu flag
* in cpu/common.c
*/
int __init notsc_setup(char *str)
{
setup_clear_cpu_cap(X86_FEATURE_TSC);
return 1;
}
#endif
__setup("notsc", notsc_setup);

86
arch/x86/kernel/tsc_32.c
View File

@ -15,52 +15,8 @@
#include "mach_timer.h"
/* native_sched_clock() is called before tsc_init(), so
we must start with the TSC soft disabled to prevent
erroneous rdtsc usage on !cpu_has_tsc processors */
static int tsc_disabled = -1;
/*
* 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;
EXPORT_SYMBOL_GPL(tsc_khz);
#ifdef CONFIG_X86_TSC
static int __init tsc_setup(char *str)
{
printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, "
"cannot disable TSC completely.\n");
tsc_disabled = 1;
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)
{
setup_clear_cpu_cap(X86_FEATURE_TSC);
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;
int check_tsc_unstable(void)
{
return tsc_unstable;
}
EXPORT_SYMBOL_GPL(check_tsc_unstable);
extern int tsc_unstable;
extern int tsc_disabled;
/* Accelerators for sched_clock()
* convert from cycles(64bits) => nanoseconds (64bits)
@ -109,44 +65,6 @@ static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
local_irq_restore(flags);
}
/*
* Scheduler clock - returns current time in nanosec units.
*/
unsigned long long native_sched_clock(void)
{
unsigned long long this_offset;
/*
* Fall back to jiffies if there's no TSC available:
* ( But note that we still use it if the TSC is marked
* unstable. We do this because unlike Time Of Day,
* the scheduler clock tolerates small errors and it's
* very important for it to be as fast as the platform
* can achive it. )
*/
if (unlikely(tsc_disabled))
/* 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);
}
/* We need to define a real function for sched_clock, to override the
weak default version */
#ifdef CONFIG_PARAVIRT
unsigned long long sched_clock(void)
{
return paravirt_sched_clock();
}
#else
unsigned long long sched_clock(void)
__attribute__((alias("native_sched_clock")));
#endif
unsigned long native_calculate_cpu_khz(void)
{
unsigned long long start, end;

67
arch/x86/kernel/tsc_64.c
View File

@ -13,12 +13,8 @@
#include <asm/timer.h>
#include <asm/vgtod.h>
static int notsc __initdata = 0;
unsigned int cpu_khz; /* TSC clocks / usec, not used here */
EXPORT_SYMBOL(cpu_khz);
unsigned int tsc_khz;
EXPORT_SYMBOL(tsc_khz);
extern int tsc_unstable;
extern int tsc_disabled;
/* Accelerators for sched_clock()
* convert from cycles(64bits) => nanoseconds (64bits)
@ -41,6 +37,7 @@ EXPORT_SYMBOL(tsc_khz);
*
* -johnstul@us.ibm.com "math is hard, lets go shopping!"
*/
DEFINE_PER_CPU(unsigned long, cyc2ns);
static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
@ -63,41 +60,6 @@ static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
local_irq_restore(flags);
}
unsigned long long native_sched_clock(void)
{
unsigned long a = 0;
/* Could do CPU core sync here. Opteron can execute rdtsc speculatively,
* which means it is not completely exact and may not be monotonous
* between CPUs. But the errors should be too small to matter for
* scheduling purposes.
*/
rdtscll(a);
return cycles_2_ns(a);
}
/* We need to define a real function for sched_clock, to override the
weak default version */
#ifdef CONFIG_PARAVIRT
unsigned long long sched_clock(void)
{
return paravirt_sched_clock();
}
#else
unsigned long long
sched_clock(void) __attribute__((alias("native_sched_clock")));
#endif
static int tsc_unstable;
int check_tsc_unstable(void)
{
return tsc_unstable;
}
EXPORT_SYMBOL_GPL(check_tsc_unstable);
#ifdef CONFIG_CPU_FREQ
/* Frequency scaling support. Adjust the TSC based timer when the cpu frequency
@ -281,14 +243,6 @@ __cpuinit int unsynchronized_tsc(void)
return num_present_cpus() > 1;
}
int __init notsc_setup(char *s)
{
notsc = 1;
return 1;
}
__setup("notsc", notsc_setup);
static struct clocksource clocksource_tsc;
/*
@ -346,12 +300,13 @@ EXPORT_SYMBOL_GPL(mark_tsc_unstable);
void __init init_tsc_clocksource(void)
{
if (!notsc) {
clocksource_tsc.mult = clocksource_khz2mult(tsc_khz,
clocksource_tsc.shift);
if (check_tsc_unstable())
clocksource_tsc.rating = 0;
if (tsc_disabled > 0)
return;
clocksource_register(&clocksource_tsc);
}
clocksource_tsc.mult = clocksource_khz2mult(tsc_khz,
clocksource_tsc.shift);
if (check_tsc_unstable())
clocksource_tsc.rating = 0;
clocksource_register(&clocksource_tsc);
}