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Commit d3fdbed9 authored by Johannes Weiner's avatar Johannes Weiner Committed by Patrick Daly
Browse files

sched: loadavg: make calc_load_n() public 

It's going to be used in a later patch. Keep the churn separate.

Link: http://lkml.kernel.org/r/20180828172258.3185-6-hannes@cmpxchg.org


Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: default avatarSuren Baghdasaryan <surenb@google.com>
Tested-by: default avatarDaniel Drake <drake@endlessm.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <jweiner@fb.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Enderborg <peter.enderborg@sony.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Change-Id: I728dca5e1b07bf9cda24c2bf4ba7521ab029ea37
Git-commit: 5c54f5b9edb1aa2eabbb1091c458f1b6776a1896
Git-repo: https://source.codeaurora.org/quic/la/kernel/msm-4.19


Signed-off-by: default avatarPatrick Daly <pdaly@codeaurora.org>
parent 5f5cfd3d

include/linux/sched/loadavg.h

+3 −0
Original line number Diff line number Diff line
@@ -37,6 +37,9 @@ calc_load(unsigned long load, unsigned long exp, unsigned long active) 
	return newload / FIXED_1;

}



extern unsigned long calc_load_n(unsigned long load, unsigned long exp,

				 unsigned long active, unsigned int n);



#define LOAD_INT(x) ((x) >> FSHIFT)

#define LOAD_FRAC(x) LOAD_INT(((x) & (FIXED_1-1)) * 100)

kernel/sched/loadavg.c

+69 −69
Original line number Diff line number Diff line
@@ -91,6 +91,75 @@ long calc_load_fold_active(struct rq *this_rq, long adjust) 
	return delta;

}



/**

 * fixed_power_int - compute: x^n, in O(log n) time

 *

 * @x:         base of the power

 * @frac_bits: fractional bits of @x

 * @n:         power to raise @x to.

 *

 * By exploiting the relation between the definition of the natural power

 * function: x^n := x*x*...*x (x multiplied by itself for n times), and

 * the binary encoding of numbers used by computers: n := \Sum n_i * 2^i,

 * (where: n_i \elem {0, 1}, the binary vector representing n),

 * we find: x^n := x^(\Sum n_i * 2^i) := \Prod x^(n_i * 2^i), which is

 * of course trivially computable in O(log_2 n), the length of our binary

 * vector.

 */

static unsigned long

fixed_power_int(unsigned long x, unsigned int frac_bits, unsigned int n)

{

	unsigned long result = 1UL << frac_bits;



	if (n) {

		for (;;) {

			if (n & 1) {

				result *= x;

				result += 1UL << (frac_bits - 1);

				result >>= frac_bits;

			}

			n >>= 1;

			if (!n)

				break;

			x *= x;

			x += 1UL << (frac_bits - 1);

			x >>= frac_bits;

		}

	}



	return result;

}



/*

 * a1 = a0 * e + a * (1 - e)

 *

 * a2 = a1 * e + a * (1 - e)

 *    = (a0 * e + a * (1 - e)) * e + a * (1 - e)

 *    = a0 * e^2 + a * (1 - e) * (1 + e)

 *

 * a3 = a2 * e + a * (1 - e)

 *    = (a0 * e^2 + a * (1 - e) * (1 + e)) * e + a * (1 - e)

 *    = a0 * e^3 + a * (1 - e) * (1 + e + e^2)

 *

 *  ...

 *

 * an = a0 * e^n + a * (1 - e) * (1 + e + ... + e^n-1) [1]

 *    = a0 * e^n + a * (1 - e) * (1 - e^n)/(1 - e)

 *    = a0 * e^n + a * (1 - e^n)

 *

 * [1] application of the geometric series:

 *

 *              n         1 - x^(n+1)

 *     S_n := \Sum x^i = -------------

 *             i=0          1 - x

 */

unsigned long

calc_load_n(unsigned long load, unsigned long exp,

	    unsigned long active, unsigned int n)

{

	return calc_load(load, fixed_power_int(exp, FSHIFT, n), active);

}



#ifdef CONFIG_NO_HZ_COMMON

/*

 * Handle NO_HZ for the global load-average.
@@ -210,75 +279,6 @@ static long calc_load_nohz_fold(void) 
	return delta;

}



/**

 * fixed_power_int - compute: x^n, in O(log n) time

 *

 * @x:         base of the power

 * @frac_bits: fractional bits of @x

 * @n:         power to raise @x to.

 *

 * By exploiting the relation between the definition of the natural power

 * function: x^n := x*x*...*x (x multiplied by itself for n times), and

 * the binary encoding of numbers used by computers: n := \Sum n_i * 2^i,

 * (where: n_i \elem {0, 1}, the binary vector representing n),

 * we find: x^n := x^(\Sum n_i * 2^i) := \Prod x^(n_i * 2^i), which is

 * of course trivially computable in O(log_2 n), the length of our binary

 * vector.

 */

static unsigned long

fixed_power_int(unsigned long x, unsigned int frac_bits, unsigned int n)

{

	unsigned long result = 1UL << frac_bits;



	if (n) {

		for (;;) {

			if (n & 1) {

				result *= x;

				result += 1UL << (frac_bits - 1);

				result >>= frac_bits;

			}

			n >>= 1;

			if (!n)

				break;

			x *= x;

			x += 1UL << (frac_bits - 1);

			x >>= frac_bits;

		}

	}



	return result;

}



/*

 * a1 = a0 * e + a * (1 - e)

 *

 * a2 = a1 * e + a * (1 - e)

 *    = (a0 * e + a * (1 - e)) * e + a * (1 - e)

 *    = a0 * e^2 + a * (1 - e) * (1 + e)

 *

 * a3 = a2 * e + a * (1 - e)

 *    = (a0 * e^2 + a * (1 - e) * (1 + e)) * e + a * (1 - e)

 *    = a0 * e^3 + a * (1 - e) * (1 + e + e^2)

 *

 *  ...

 *

 * an = a0 * e^n + a * (1 - e) * (1 + e + ... + e^n-1) [1]

 *    = a0 * e^n + a * (1 - e) * (1 - e^n)/(1 - e)

 *    = a0 * e^n + a * (1 - e^n)

 *

 * [1] application of the geometric series:

 *

 *              n         1 - x^(n+1)

 *     S_n := \Sum x^i = -------------

 *             i=0          1 - x

 */

static unsigned long

calc_load_n(unsigned long load, unsigned long exp,

	    unsigned long active, unsigned int n)

{

	return calc_load(load, fixed_power_int(exp, FSHIFT, n), active);

}



/*

 * NO_HZ can leave us missing all per-CPU ticks calling

 * calc_load_fold_active(), but since a NO_HZ CPU folds its delta into