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    Subject[patch 14/21] Introduce ktime_t time format

    - introduce ktime_t: nanosecond-resolution time format.

    - eliminate the plain s64 scalar type, and always use the union.
    This simplifies the arithmetics. Idea from Roman Zippel.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>

    arch/i386/Kconfig | 4
    include/linux/ktime.h | 269 ++++++++++++++++++++++++++++++++++++++++++++++++++
    2 files changed, 273 insertions(+)

    Index: linux-2.6.15-rc5/arch/i386/Kconfig
    ===================================================================
    --- linux-2.6.15-rc5.orig/arch/i386/Kconfig
    +++ linux-2.6.15-rc5/arch/i386/Kconfig
    @@ -1055,3 +1055,7 @@ config X86_TRAMPOLINE
    bool
    depends on X86_SMP || (X86_VOYAGER && SMP)
    default y
    +
    +config KTIME_SCALAR
    + bool
    + default y
    Index: linux-2.6.15-rc5/include/linux/ktime.h
    ===================================================================
    --- /dev/null
    +++ linux-2.6.15-rc5/include/linux/ktime.h
    @@ -0,0 +1,269 @@
    +/*
    + * include/linux/ktime.h
    + *
    + * ktime_t - nanosecond-resolution time format.
    + *
    + * Copyright(C) 2005, Thomas Gleixner <tglx@linutronix.de>
    + * Copyright(C) 2005, Red Hat, Inc., Ingo Molnar
    + *
    + * data type definitions, declarations, prototypes and macros.
    + *
    + * Started by: Thomas Gleixner and Ingo Molnar
    + *
    + * For licencing details see kernel-base/COPYING
    + */
    +#ifndef _LINUX_KTIME_H
    +#define _LINUX_KTIME_H
    +
    +#include <linux/time.h>
    +#include <linux/jiffies.h>
    +
    +/*
    + * ktime_t:
    + *
    + * On 64-bit CPUs a single 64-bit variable is used to store the hrtimers
    + * internal representation of time values in scalar nanoseconds. The
    + * design plays out best on 64-bit CPUs, where most conversions are
    + * NOPs and most arithmetic ktime_t operations are plain arithmetic
    + * operations.
    + *
    + * On 32-bit CPUs an optimized representation of the timespec structure
    + * is used to avoid expensive conversions from and to timespecs. The
    + * endian-aware order of the tv struct members is choosen to allow
    + * mathematical operations on the tv64 member of the union too, which
    + * for certain operations produces better code.
    + *
    + * For architectures with efficient support for 64/32-bit conversions the
    + * plain scalar nanosecond based representation can be selected by the
    + * config switch CONFIG_KTIME_SCALAR.
    + */
    +typedef union {
    + s64 tv64;
    +#if BITS_PER_LONG != 64 && !defined(CONFIG_KTIME_SCALAR)
    + struct {
    +# ifdef __BIG_ENDIAN
    + s32 sec, nsec;
    +# else
    + s32 nsec, sec;
    +# endif
    + } tv;
    +#endif
    +} ktime_t;
    +
    +#define KTIME_MAX (~((u64)1 << 63))
    +
    +/*
    + * ktime_t definitions when using the 64-bit scalar representation:
    + */
    +
    +#if (BITS_PER_LONG == 64) || defined(CONFIG_KTIME_SCALAR)
    +
    +/* Define a ktime_t variable and initialize it to zero: */
    +#define DEFINE_KTIME(kt) ktime_t kt = { .tv64 = 0 }
    +
    +/**
    + * ktime_set - Set a ktime_t variable from a seconds/nanoseconds value
    + *
    + * @secs: seconds to set
    + * @nsecs: nanoseconds to set
    + *
    + * Return the ktime_t representation of the value
    + */
    +static inline ktime_t ktime_set(const long secs, const unsigned long nsecs)
    +{
    + return (ktime_t) { .tv64 = (s64)secs * NSEC_PER_SEC + (s64)nsecs };
    +}
    +
    +/* Subtract two ktime_t variables. rem = lhs -rhs: */
    +#define ktime_sub(lhs, rhs) \
    + ({ (ktime_t){ .tv64 = (lhs).tv64 - (rhs).tv64 }; })
    +
    +/* Add two ktime_t variables. res = lhs + rhs: */
    +#define ktime_add(lhs, rhs) \
    + ({ (ktime_t){ .tv64 = (lhs).tv64 + (rhs).tv64 }; })
    +
    +/*
    + * Add a ktime_t variable and a scalar nanosecond value.
    + * res = kt + nsval:
    + */
    +#define ktime_add_ns(kt, nsval) \
    + ({ (ktime_t){ .tv64 = (kt).tv64 + (nsval) }; })
    +
    +/* convert a timespec to ktime_t format: */
    +#define timespec_to_ktime(ts) ktime_set((ts).tv_sec, (ts).tv_nsec)
    +
    +/* convert a timeval to ktime_t format: */
    +#define timeval_to_ktime(tv) ktime_set((tv).tv_sec, (tv).tv_usec * 1000)
    +
    +/* Map the ktime_t to timespec conversion to ns_to_timespec function */
    +#define ktime_to_timespec(kt) ns_to_timespec((kt).tv64)
    +
    +/* Map the ktime_t to timeval conversion to ns_to_timeval function */
    +#define ktime_to_timeval(kt) ns_to_timeval((kt).tv64)
    +
    +/* Map the ktime_t to clock_t conversion to the inline in jiffies.h: */
    +#define ktime_to_clock_t(kt) nsec_to_clock_t((kt).tv64)
    +
    +/* Convert ktime_t to nanoseconds - NOP in the scalar storage format: */
    +#define ktime_to_ns(kt) ((kt).tv64)
    +
    +#else
    +
    +/*
    + * Helper macros/inlines to get the ktime_t math right in the timespec
    + * representation. The macros are sometimes ugly - their actual use is
    + * pretty okay-ish, given the circumstances. We do all this for
    + * performance reasons. The pure scalar nsec_t based code was nice and
    + * simple, but created too many 64-bit / 32-bit conversions and divisions.
    + *
    + * Be especially aware that negative values are represented in a way
    + * that the tv.sec field is negative and the tv.nsec field is greater
    + * or equal to zero but less than nanoseconds per second. This is the
    + * same representation which is used by timespecs.
    + *
    + * tv.sec < 0 and 0 >= tv.nsec < NSEC_PER_SEC
    + */
    +
    +/* Define a ktime_t variable and initialize it to zero: */
    +#define DEFINE_KTIME(kt) ktime_t kt = { .tv64 = 0 }
    +
    +/* Set a ktime_t variable to a value in sec/nsec representation: */
    +static inline ktime_t ktime_set(const long secs, const unsigned long nsecs)
    +{
    + return (ktime_t) { .tv = { .sec = secs, .nsec = nsecs } };
    +}
    +
    +/**
    + * ktime_sub - subtract two ktime_t variables
    + *
    + * @lhs: minuend
    + * @rhs: subtrahend
    + *
    + * Returns the remainder of the substraction
    + */
    +static inline ktime_t ktime_sub(const ktime_t lhs, const ktime_t rhs)
    +{
    + ktime_t res;
    +
    + res.tv64 = lhs.tv64 - rhs.tv64;
    + if (res.tv.nsec < 0)
    + res.tv.nsec += NSEC_PER_SEC;
    +
    + return res;
    +}
    +
    +/**
    + * ktime_add - add two ktime_t variables
    + *
    + * @add1: addend1
    + * @add2: addend2
    + *
    + * Returns the sum of addend1 and addend2
    + */
    +static inline ktime_t ktime_add(const ktime_t add1, const ktime_t add2)
    +{
    + ktime_t res;
    +
    + res.tv64 = add1.tv64 + add2.tv64;
    + /*
    + * performance trick: the (u32) -NSEC gives 0x00000000Fxxxxxxx
    + * so we subtract NSEC_PER_SEC and add 1 to the upper 32 bit.
    + *
    + * it's equivalent to:
    + * tv.nsec -= NSEC_PER_SEC
    + * tv.sec ++;
    + */
    + if (res.tv.nsec >= NSEC_PER_SEC)
    + res.tv64 += (u32)-NSEC_PER_SEC;
    +
    + return res;
    +}
    +
    +/**
    + * ktime_add_ns - Add a scalar nanoseconds value to a ktime_t variable
    + *
    + * @kt: addend
    + * @nsec: the scalar nsec value to add
    + *
    + * Returns the sum of kt and nsec in ktime_t format
    + */
    +extern ktime_t ktime_add_ns(const ktime_t kt, u64 nsec);
    +
    +/**
    + * timespec_to_ktime - convert a timespec to ktime_t format
    + *
    + * @ts: the timespec variable to convert
    + *
    + * Returns a ktime_t variable with the converted timespec value
    + */
    +static inline ktime_t timespec_to_ktime(const struct timespec ts)
    +{
    + return (ktime_t) { .tv = { .sec = (s32)ts.tv_sec,
    + .nsec = (s32)ts.tv_nsec } };
    +}
    +
    +/**
    + * timeval_to_ktime - convert a timeval to ktime_t format
    + *
    + * @tv: the timeval variable to convert
    + *
    + * Returns a ktime_t variable with the converted timeval value
    + */
    +static inline ktime_t timeval_to_ktime(const struct timeval tv)
    +{
    + return (ktime_t) { .tv = { .sec = (s32)tv.tv_sec,
    + .nsec = (s32)tv.tv_usec * 1000 } };
    +}
    +
    +/**
    + * ktime_to_timespec - convert a ktime_t variable to timespec format
    + *
    + * @kt: the ktime_t variable to convert
    + *
    + * Returns the timespec representation of the ktime value
    + */
    +static inline struct timespec ktime_to_timespec(const ktime_t kt)
    +{
    + return (struct timespec) { .tv_sec = (time_t) kt.tv.sec,
    + .tv_nsec = (long) kt.tv.nsec };
    +}
    +
    +/**
    + * ktime_to_timeval - convert a ktime_t variable to timeval format
    + *
    + * @kt: the ktime_t variable to convert
    + *
    + * Returns the timeval representation of the ktime value
    + */
    +static inline struct timeval ktime_to_timeval(const ktime_t kt)
    +{
    + return (struct timeval) {
    + .tv_sec = (time_t) kt.tv.sec,
    + .tv_usec = (suseconds_t) (kt.tv.nsec / NSEC_PER_USEC) };
    +}
    +
    +/**
    + * ktime_to_clock_t - convert a ktime_t variable to clock_t format
    + * @kt: the ktime_t variable to convert
    + *
    + * Returns a clock_t variable with the converted value
    + */
    +static inline clock_t ktime_to_clock_t(const ktime_t kt)
    +{
    + return nsec_to_clock_t( (u64) kt.tv.sec * NSEC_PER_SEC + kt.tv.nsec);
    +}
    +
    +/**
    + * ktime_to_ns - convert a ktime_t variable to scalar nanoseconds
    + * @kt: the ktime_t variable to convert
    + *
    + * Returns the scalar nanoseconds representation of kt
    + */
    +static inline u64 ktime_to_ns(const ktime_t kt)
    +{
    + return (u64) kt.tv.sec * NSEC_PER_SEC + kt.tv.nsec;
    +}
    +
    +#endif
    +
    +#endif
    --

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