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math64: New div64_u64_rem helper

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Provide an extended version of div64_u64() that
also returns the remainder of the division.

We are going to need this to refine the cputime
scaling code.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Frederic Weisbecker 2013-03-05 18:05:46 +01:00
parent 660cc00f8c
commit f792685006
2 changed files with 31 additions and 7 deletions
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19
include/linux/math64.h
View File

@ -29,6 +29,15 @@ static inline s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
return dividend / divisor;
}
/**
* div64_u64_rem - unsigned 64bit divide with 64bit divisor
*/
static inline u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
{
*remainder = dividend % divisor;
return dividend / divisor;
}
/**
* div64_u64 - unsigned 64bit divide with 64bit divisor
*/
@ -61,8 +70,16 @@ static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder)
extern s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder);
#endif
#ifndef div64_u64_rem
extern u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder);
#endif
#ifndef div64_u64
extern u64 div64_u64(u64 dividend, u64 divisor);
static inline u64 div64_u64(u64 dividend, u64 divisor)
{
u64 remainder;
return div64_u64_rem(dividend, divisor, &remainder);
}
#endif
#ifndef div64_s64

19
lib/div64.c
View File

@ -79,9 +79,10 @@ EXPORT_SYMBOL(div_s64_rem);
#endif
/**
* div64_u64 - unsigned 64bit divide with 64bit divisor
* div64_u64_rem - unsigned 64bit divide with 64bit divisor and 64bit remainder
* @dividend: 64bit dividend
* @divisor: 64bit divisor
* @remainder: 64bit remainder
*
* This implementation is a modified version of the algorithm proposed
* by the book 'Hacker's Delight'. The original source and full proof
@ -89,27 +90,33 @@ EXPORT_SYMBOL(div_s64_rem);
*
* 'http://www.hackersdelight.org/HDcode/newCode/divDouble.c.txt'
*/
#ifndef div64_u64
u64 div64_u64(u64 dividend, u64 divisor)
#ifndef div64_u64_rem
u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
{
u32 high = divisor >> 32;
u64 quot;
if (high == 0) {
quot = div_u64(dividend, divisor);
u32 rem32;
quot = div_u64_rem(dividend, divisor, &rem32);
*remainder = rem32;
} else {
int n = 1 + fls(high);
quot = div_u64(dividend >> n, divisor >> n);
if (quot != 0)
quot--;
if ((dividend - quot * divisor) >= divisor)
*remainder = dividend - quot * divisor;
if (*remainder >= divisor) {
quot++;
*remainder -= divisor;
}
}
return quot;
}
EXPORT_SYMBOL(div64_u64);
EXPORT_SYMBOL(div64_u64_rem);
#endif
/**