diff options
| -rw-r--r-- | arch/x86/xen/time.c | 13 | ||||
| -rw-r--r-- | include/linux/math64.h | 21 | ||||
| -rw-r--r-- | include/linux/time.h | 16 | ||||
| -rw-r--r-- | lib/div64.c | 10 |
4 files changed, 40 insertions, 20 deletions
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c index c39e1a5aa24..52b2e385698 100644 --- a/arch/x86/xen/time.c +++ b/arch/x86/xen/time.c @@ -12,6 +12,7 @@ #include <linux/clocksource.h> #include <linux/clockchips.h> #include <linux/kernel_stat.h> +#include <linux/math64.h> #include <asm/xen/hypervisor.h> #include <asm/xen/hypercall.h> @@ -150,11 +151,7 @@ static void do_stolen_accounting(void) if (stolen < 0) stolen = 0; - ticks = 0; - while (stolen >= NS_PER_TICK) { - ticks++; - stolen -= NS_PER_TICK; - } + ticks = iter_div_u64_rem(stolen, NS_PER_TICK, &stolen); __get_cpu_var(residual_stolen) = stolen; account_steal_time(NULL, ticks); @@ -166,11 +163,7 @@ static void do_stolen_accounting(void) if (blocked < 0) blocked = 0; - ticks = 0; - while (blocked >= NS_PER_TICK) { - ticks++; - blocked -= NS_PER_TICK; - } + ticks = iter_div_u64_rem(blocked, NS_PER_TICK, &blocked); __get_cpu_var(residual_blocked) = blocked; account_steal_time(idle_task(smp_processor_id()), ticks); } diff --git a/include/linux/math64.h b/include/linux/math64.h index c1a5f81501f..c87f1528703 100644 --- a/include/linux/math64.h +++ b/include/linux/math64.h @@ -81,4 +81,25 @@ static inline s64 div_s64(s64 dividend, s32 divisor) } #endif +u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder); + +static __always_inline u32 +__iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder) +{ + u32 ret = 0; + + while (dividend >= divisor) { + /* The following asm() prevents the compiler from + optimising this loop into a modulo operation. */ + asm("" : "+rm"(dividend)); + + dividend -= divisor; + ret++; + } + + *remainder = dividend; + + return ret; +} + #endif /* _LINUX_MATH64_H */ diff --git a/include/linux/time.h b/include/linux/time.h index d32ef0ad4c0..e15206a7e82 100644 --- a/include/linux/time.h +++ b/include/linux/time.h @@ -6,6 +6,7 @@ #ifdef __KERNEL__ # include <linux/cache.h> # include <linux/seqlock.h> +# include <linux/math64.h> #endif #ifndef _STRUCT_TIMESPEC @@ -169,18 +170,13 @@ extern struct timeval ns_to_timeval(const s64 nsec); * timespec_add_ns - Adds nanoseconds to a timespec * @a: pointer to timespec to be incremented * @ns: unsigned nanoseconds value to be added + * + * This must always be inlined because its used from the x86-64 vdso, + * which cannot call other kernel functions. */ -static inline void timespec_add_ns(struct timespec *a, u64 ns) +static __always_inline void timespec_add_ns(struct timespec *a, u64 ns) { - ns += a->tv_nsec; - while(unlikely(ns >= NSEC_PER_SEC)) { - /* The following asm() prevents the compiler from - * optimising this loop into a modulo operation. */ - asm("" : "+r"(ns)); - - ns -= NSEC_PER_SEC; - a->tv_sec++; - } + a->tv_sec += __iter_div_u64_rem(a->tv_nsec + ns, NSEC_PER_SEC, &ns); a->tv_nsec = ns; } #endif /* __KERNEL__ */ diff --git a/lib/div64.c b/lib/div64.c index bb5bd0c0f03..a111eb8de9c 100644 --- a/lib/div64.c +++ b/lib/div64.c @@ -98,3 +98,13 @@ EXPORT_SYMBOL(div64_u64); #endif #endif /* BITS_PER_LONG == 32 */ + +/* + * Iterative div/mod for use when dividend is not expected to be much + * bigger than divisor. + */ +u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder) +{ + return __iter_div_u64_rem(dividend, divisor, remainder); +} +EXPORT_SYMBOL(iter_div_u64_rem); |