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remarkable-linux/arch/powerpc/include/asm/time.h
Paul Mackerras cf9efce0ce powerpc: Account time using timebase rather than PURR 
Currently, when CONFIG_VIRT_CPU_ACCOUNTING is enabled, we use the
PURR register for measuring the user and system time used by
processes, as well as other related times such as hardirq and
softirq times.  This turns out to be quite confusing for users
because it means that a program will often be measured as taking
less time when run on a multi-threaded processor (SMT2 or SMT4 mode)
than it does when run on a single-threaded processor (ST mode), even
though the program takes longer to finish.  The discrepancy is
accounted for as stolen time, which is also confusing, particularly
when there are no other partitions running.

This changes the accounting to use the timebase instead, meaning that
the reported user and system times are the actual number of real-time
seconds that the program was executing on the processor thread,
regardless of which SMT mode the processor is in.  Thus a program will
generally show greater user and system times when run on a
multi-threaded processor than on a single-threaded processor.

On pSeries systems on POWER5 or later processors, we measure the
stolen time (time when this partition wasn't running) using the
hypervisor dispatch trace log.  We check for new entries in the
log on every entry from user mode and on every transition from
kernel process context to soft or hard IRQ context (i.e. when
account_system_vtime() gets called).  So that we can correctly
distinguish time stolen from user time and time stolen from system
time, without having to check the log on every exit to user mode,
we store separate timestamps for exit to user mode and entry from
user mode.

On systems that have a SPURR (POWER6 and POWER7), we read the SPURR
in account_system_vtime() (as before), and then apportion the SPURR
ticks since the last time we read it between scaled user time and
scaled system time according to the relative proportions of user
time and system time over the same interval.  This avoids having to
read the SPURR on every kernel entry and exit.  On systems that have
PURR but not SPURR (i.e., POWER5), we do the same using the PURR
rather than the SPURR.

This disables the DTL user interface in /sys/debug/kernel/powerpc/dtl
for now since it conflicts with the use of the dispatch trace log
by the time accounting code.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2010-09-02 14:07:31 +10:00

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/*
* Common time prototypes and such for all ppc machines.
*
* Written by Cort Dougan (cort@cs.nmt.edu) to merge
* Paul Mackerras' version and mine for PReP and Pmac.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#ifndef __POWERPC_TIME_H
#define __POWERPC_TIME_H
#ifdef __KERNEL__
#include <linux/types.h>
#include <linux/percpu.h>
#include <asm/processor.h>
#ifdef CONFIG_PPC_ISERIES
#include <asm/paca.h>
#include <asm/firmware.h>
#include <asm/iseries/hv_call.h>
#endif
/* time.c */
extern unsigned long tb_ticks_per_jiffy;
extern unsigned long tb_ticks_per_usec;
extern unsigned long tb_ticks_per_sec;
struct rtc_time;
extern void to_tm(int tim, struct rtc_time * tm);
extern void GregorianDay(struct rtc_time *tm);
extern void generic_calibrate_decr(void);
extern void set_dec_cpu6(unsigned int val);
/* Some sane defaults: 125 MHz timebase, 1GHz processor */
extern unsigned long ppc_proc_freq;
#define DEFAULT_PROC_FREQ (DEFAULT_TB_FREQ * 8)
extern unsigned long ppc_tb_freq;
#define DEFAULT_TB_FREQ 125000000UL
struct div_result {
u64 result_high;
u64 result_low;
};
/* Accessor functions for the timebase (RTC on 601) registers. */
/* If one day CONFIG_POWER is added just define __USE_RTC as 1 */
#ifdef CONFIG_6xx
#define __USE_RTC() (!cpu_has_feature(CPU_FTR_USE_TB))
#else
#define __USE_RTC() 0
#endif
#ifdef CONFIG_PPC64
/* For compatibility, get_tbl() is defined as get_tb() on ppc64 */
#define get_tbl get_tb
#else
static inline unsigned long get_tbl(void)
{
#if defined(CONFIG_403GCX)
unsigned long tbl;
asm volatile("mfspr %0, 0x3dd" : "=r" (tbl));
return tbl;
#else
return mftbl();
#endif
}
static inline unsigned int get_tbu(void)
{
#ifdef CONFIG_403GCX
unsigned int tbu;
asm volatile("mfspr %0, 0x3dc" : "=r" (tbu));
return tbu;
#else
return mftbu();
#endif
}
#endif /* !CONFIG_PPC64 */
static inline unsigned int get_rtcl(void)
{
unsigned int rtcl;
asm volatile("mfrtcl %0" : "=r" (rtcl));
return rtcl;
}
static inline u64 get_rtc(void)
{
unsigned int hi, lo, hi2;
do {
asm volatile("mfrtcu %0; mfrtcl %1; mfrtcu %2"
: "=r" (hi), "=r" (lo), "=r" (hi2));
} while (hi2 != hi);
return (u64)hi * 1000000000 + lo;
}
#ifdef CONFIG_PPC64
static inline u64 get_tb(void)
{
return mftb();
}
#else /* CONFIG_PPC64 */
static inline u64 get_tb(void)
{
unsigned int tbhi, tblo, tbhi2;
do {
tbhi = get_tbu();
tblo = get_tbl();
tbhi2 = get_tbu();
} while (tbhi != tbhi2);
return ((u64)tbhi << 32) | tblo;
}
#endif /* !CONFIG_PPC64 */
static inline u64 get_tb_or_rtc(void)
{
return __USE_RTC() ? get_rtc() : get_tb();
}
static inline void set_tb(unsigned int upper, unsigned int lower)
{
mtspr(SPRN_TBWL, 0);
mtspr(SPRN_TBWU, upper);
mtspr(SPRN_TBWL, lower);
}
/* Accessor functions for the decrementer register.
* The 4xx doesn't even have a decrementer. I tried to use the
* generic timer interrupt code, which seems OK, with the 4xx PIT
* in auto-reload mode. The problem is PIT stops counting when it
* hits zero. If it would wrap, we could use it just like a decrementer.
*/
static inline unsigned int get_dec(void)
{
#if defined(CONFIG_40x)
return (mfspr(SPRN_PIT));
#else
return (mfspr(SPRN_DEC));
#endif
}
/*
* Note: Book E and 4xx processors differ from other PowerPC processors
* in when the decrementer generates its interrupt: on the 1 to 0
* transition for Book E/4xx, but on the 0 to -1 transition for others.
*/
static inline void set_dec(int val)
{
#if defined(CONFIG_40x)
mtspr(SPRN_PIT, val);
#elif defined(CONFIG_8xx_CPU6)
set_dec_cpu6(val - 1);
#else
#ifndef CONFIG_BOOKE
--val;
#endif
#ifdef CONFIG_PPC_ISERIES
if (firmware_has_feature(FW_FEATURE_ISERIES) &&
get_lppaca()->shared_proc) {
get_lppaca()->virtual_decr = val;
if (get_dec() > val)
HvCall_setVirtualDecr();
return;
}
#endif
mtspr(SPRN_DEC, val);
#endif /* not 40x or 8xx_CPU6 */
}
static inline unsigned long tb_ticks_since(unsigned long tstamp)
{
if (__USE_RTC()) {
int delta = get_rtcl() - (unsigned int) tstamp;
return delta < 0 ? delta + 1000000000 : delta;
}
return get_tbl() - tstamp;
}
#define mulhwu(x,y) \
({unsigned z; asm ("mulhwu %0,%1,%2" : "=r" (z) : "r" (x), "r" (y)); z;})
#ifdef CONFIG_PPC64
#define mulhdu(x,y) \
({unsigned long z; asm ("mulhdu %0,%1,%2" : "=r" (z) : "r" (x), "r" (y)); z;})
#else
extern u64 mulhdu(u64, u64);
#endif
extern void div128_by_32(u64 dividend_high, u64 dividend_low,
unsigned divisor, struct div_result *dr);
/* Used to store Processor Utilization register (purr) values */
struct cpu_usage {
u64 current_tb; /* Holds the current purr register values */
};
DECLARE_PER_CPU(struct cpu_usage, cpu_usage_array);
#if defined(CONFIG_VIRT_CPU_ACCOUNTING)
#define account_process_vtime(tsk) account_process_tick(tsk, 0)
#else
#define account_process_vtime(tsk) do { } while (0)
#endif
extern void secondary_cpu_time_init(void);
extern void iSeries_time_init_early(void);
#endif /* __KERNEL__ */
#endif /* __POWERPC_TIME_H */
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