[PATCH RFC] lib: proportions: Remove unused code.

[Richard Cochran]

By accident I stumbled across code that is no longer used.  According
to git grep, the global functions in lib/proportions.c are not used
anywhere.  This patch removes the old, unused code.

Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Richard Cochran <rcochran@xxxxxxxxxxxxx>
---
 include/linux/proportions.h | 137 ---------------
 include/linux/sched.h       |   1 -
 lib/Makefile                |   2 +-
 lib/proportions.c           | 407 --------------------------------------------
 4 files changed, 1 insertion(+), 546 deletions(-)
 delete mode 100644 include/linux/proportions.h
 delete mode 100644 lib/proportions.c

diff --git a/include/linux/proportions.h b/include/linux/proportions.h
deleted file mode 100644
index 2122133..0000000
--- a/include/linux/proportions.h
+++ /dev/null
@@ -1,137 +0,0 @@
-/*
- * FLoating proportions
- *
- *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
- *
- * This file contains the public data structure and API definitions.
- */
-
-#ifndef _LINUX_PROPORTIONS_H
-#define _LINUX_PROPORTIONS_H
-
-#include <linux/percpu_counter.h>
-#include <linux/spinlock.h>
-#include <linux/mutex.h>
-#include <linux/gfp.h>
-
-struct prop_global {
-	/*
-	 * The period over which we differentiate
-	 *
-	 *   period = 2^shift
-	 */
-	int shift;
-	/*
-	 * The total event counter aka 'time'.
-	 *
-	 * Treated as an unsigned long; the lower 'shift - 1' bits are the
-	 * counter bits, the remaining upper bits the period counter.
-	 */
-	struct percpu_counter events;
-};
-
-/*
- * global proportion descriptor
- *
- * this is needed to consistently flip prop_global structures.
- */
-struct prop_descriptor {
-	int index;
-	struct prop_global pg[2];
-	struct mutex mutex;		/* serialize the prop_global switch */
-};
-
-int prop_descriptor_init(struct prop_descriptor *pd, int shift, gfp_t gfp);
-void prop_change_shift(struct prop_descriptor *pd, int new_shift);
-
-/*
- * ----- PERCPU ------
- */
-
-struct prop_local_percpu {
-	/*
-	 * the local events counter
-	 */
-	struct percpu_counter events;
-
-	/*
-	 * snapshot of the last seen global state
-	 */
-	int shift;
-	unsigned long period;
-	raw_spinlock_t lock;		/* protect the snapshot state */
-};
-
-int prop_local_init_percpu(struct prop_local_percpu *pl, gfp_t gfp);
-void prop_local_destroy_percpu(struct prop_local_percpu *pl);
-void __prop_inc_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl);
-void prop_fraction_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl,
-		long *numerator, long *denominator);
-
-static inline
-void prop_inc_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl)
-{
-	unsigned long flags;
-
-	local_irq_save(flags);
-	__prop_inc_percpu(pd, pl);
-	local_irq_restore(flags);
-}
-
-/*
- * Limit the time part in order to ensure there are some bits left for the
- * cycle counter and fraction multiply.
- */
-#if BITS_PER_LONG == 32
-#define PROP_MAX_SHIFT (3*BITS_PER_LONG/4)
-#else
-#define PROP_MAX_SHIFT (BITS_PER_LONG/2)
-#endif
-
-#define PROP_FRAC_SHIFT		(BITS_PER_LONG - PROP_MAX_SHIFT - 1)
-#define PROP_FRAC_BASE		(1UL << PROP_FRAC_SHIFT)
-
-void __prop_inc_percpu_max(struct prop_descriptor *pd,
-			   struct prop_local_percpu *pl, long frac);
-
-
-/*
- * ----- SINGLE ------
- */
-
-struct prop_local_single {
-	/*
-	 * the local events counter
-	 */
-	unsigned long events;
-
-	/*
-	 * snapshot of the last seen global state
-	 * and a lock protecting this state
-	 */
-	unsigned long period;
-	int shift;
-	raw_spinlock_t lock;		/* protect the snapshot state */
-};
-
-#define INIT_PROP_LOCAL_SINGLE(name)			\
-{	.lock = __RAW_SPIN_LOCK_UNLOCKED(name.lock),	\
-}
-
-int prop_local_init_single(struct prop_local_single *pl);
-void prop_local_destroy_single(struct prop_local_single *pl);
-void __prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl);
-void prop_fraction_single(struct prop_descriptor *pd, struct prop_local_single *pl,
-		long *numerator, long *denominator);
-
-static inline
-void prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl)
-{
-	unsigned long flags;
-
-	local_irq_save(flags);
-	__prop_inc_single(pd, pl);
-	local_irq_restore(flags);
-}
-
-#endif /* _LINUX_PROPORTIONS_H */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 60bba7e..6dd25d1 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -40,7 +40,6 @@ struct sched_param {
 #include <linux/pid.h>
 #include <linux/percpu.h>
 #include <linux/topology.h>
-#include <linux/proportions.h>
 #include <linux/seccomp.h>
 #include <linux/rcupdate.h>
 #include <linux/rculist.h>
diff --git a/lib/Makefile b/lib/Makefile
index 7bd6fd4..a65e9a8 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -23,7 +23,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
 	 rbtree.o radix-tree.o dump_stack.o timerqueue.o\
 	 idr.o int_sqrt.o extable.o \
 	 sha1.o md5.o irq_regs.o argv_split.o \
-	 proportions.o flex_proportions.o ratelimit.o show_mem.o \
+	 flex_proportions.o ratelimit.o show_mem.o \
 	 is_single_threaded.o plist.o decompress.o kobject_uevent.o \
 	 earlycpio.o seq_buf.o nmi_backtrace.o
 
diff --git a/lib/proportions.c b/lib/proportions.c
deleted file mode 100644
index efa54f25..0000000
--- a/lib/proportions.c
+++ /dev/null
@@ -1,407 +0,0 @@
-/*
- * Floating proportions
- *
- *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
- *
- * Description:
- *
- * The floating proportion is a time derivative with an exponentially decaying
- * history:
- *
- *   p_{j} = \Sum_{i=0} (dx_{j}/dt_{-i}) / 2^(1+i)
- *
- * Where j is an element from {prop_local}, x_{j} is j's number of events,
- * and i the time period over which the differential is taken. So d/dt_{-i} is
- * the differential over the i-th last period.
- *
- * The decaying history gives smooth transitions. The time differential carries
- * the notion of speed.
- *
- * The denominator is 2^(1+i) because we want the series to be normalised, ie.
- *
- *   \Sum_{i=0} 1/2^(1+i) = 1
- *
- * Further more, if we measure time (t) in the same events as x; so that:
- *
- *   t = \Sum_{j} x_{j}
- *
- * we get that:
- *
- *   \Sum_{j} p_{j} = 1
- *
- * Writing this in an iterative fashion we get (dropping the 'd's):
- *
- *   if (++x_{j}, ++t > period)
- *     t /= 2;
- *     for_each (j)
- *       x_{j} /= 2;
- *
- * so that:
- *
- *   p_{j} = x_{j} / t;
- *
- * We optimize away the '/= 2' for the global time delta by noting that:
- *
- *   if (++t > period) t /= 2:
- *
- * Can be approximated by:
- *
- *   period/2 + (++t % period/2)
- *
- * [ Furthermore, when we choose period to be 2^n it can be written in terms of
- *   binary operations and wraparound artefacts disappear. ]
- *
- * Also note that this yields a natural counter of the elapsed periods:
- *
- *   c = t / (period/2)
- *
- * [ Its monotonic increasing property can be applied to mitigate the wrap-
- *   around issue. ]
- *
- * This allows us to do away with the loop over all prop_locals on each period
- * expiration. By remembering the period count under which it was last accessed
- * as c_{j}, we can obtain the number of 'missed' cycles from:
- *
- *   c - c_{j}
- *
- * We can then lazily catch up to the global period count every time we are
- * going to use x_{j}, by doing:
- *
- *   x_{j} /= 2^(c - c_{j}), c_{j} = c
- */
-
-#include <linux/proportions.h>
-#include <linux/rcupdate.h>
-
-int prop_descriptor_init(struct prop_descriptor *pd, int shift, gfp_t gfp)
-{
-	int err;
-
-	if (shift > PROP_MAX_SHIFT)
-		shift = PROP_MAX_SHIFT;
-
-	pd->index = 0;
-	pd->pg[0].shift = shift;
-	mutex_init(&pd->mutex);
-	err = percpu_counter_init(&pd->pg[0].events, 0, gfp);
-	if (err)
-		goto out;
-
-	err = percpu_counter_init(&pd->pg[1].events, 0, gfp);
-	if (err)
-		percpu_counter_destroy(&pd->pg[0].events);
-
-out:
-	return err;
-}
-
-/*
- * We have two copies, and flip between them to make it seem like an atomic
- * update. The update is not really atomic wrt the events counter, but
- * it is internally consistent with the bit layout depending on shift.
- *
- * We copy the events count, move the bits around and flip the index.
- */
-void prop_change_shift(struct prop_descriptor *pd, int shift)
-{
-	int index;
-	int offset;
-	u64 events;
-	unsigned long flags;
-
-	if (shift > PROP_MAX_SHIFT)
-		shift = PROP_MAX_SHIFT;
-
-	mutex_lock(&pd->mutex);
-
-	index = pd->index ^ 1;
-	offset = pd->pg[pd->index].shift - shift;
-	if (!offset)
-		goto out;
-
-	pd->pg[index].shift = shift;
-
-	local_irq_save(flags);
-	events = percpu_counter_sum(&pd->pg[pd->index].events);
-	if (offset < 0)
-		events <<= -offset;
-	else
-		events >>= offset;
-	percpu_counter_set(&pd->pg[index].events, events);
-
-	/*
-	 * ensure the new pg is fully written before the switch
-	 */
-	smp_wmb();
-	pd->index = index;
-	local_irq_restore(flags);
-
-	synchronize_rcu();
-
-out:
-	mutex_unlock(&pd->mutex);
-}
-
-/*
- * wrap the access to the data in an rcu_read_lock() section;
- * this is used to track the active references.
- */
-static struct prop_global *prop_get_global(struct prop_descriptor *pd)
-__acquires(RCU)
-{
-	int index;
-
-	rcu_read_lock();
-	index = pd->index;
-	/*
-	 * match the wmb from vcd_flip()
-	 */
-	smp_rmb();
-	return &pd->pg[index];
-}
-
-static void prop_put_global(struct prop_descriptor *pd, struct prop_global *pg)
-__releases(RCU)
-{
-	rcu_read_unlock();
-}
-
-static void
-prop_adjust_shift(int *pl_shift, unsigned long *pl_period, int new_shift)
-{
-	int offset = *pl_shift - new_shift;
-
-	if (!offset)
-		return;
-
-	if (offset < 0)
-		*pl_period <<= -offset;
-	else
-		*pl_period >>= offset;
-
-	*pl_shift = new_shift;
-}
-
-/*
- * PERCPU
- */
-
-#define PROP_BATCH (8*(1+ilog2(nr_cpu_ids)))
-
-int prop_local_init_percpu(struct prop_local_percpu *pl, gfp_t gfp)
-{
-	raw_spin_lock_init(&pl->lock);
-	pl->shift = 0;
-	pl->period = 0;
-	return percpu_counter_init(&pl->events, 0, gfp);
-}
-
-void prop_local_destroy_percpu(struct prop_local_percpu *pl)
-{
-	percpu_counter_destroy(&pl->events);
-}
-
-/*
- * Catch up with missed period expirations.
- *
- *   until (c_{j} == c)
- *     x_{j} -= x_{j}/2;
- *     c_{j}++;
- */
-static
-void prop_norm_percpu(struct prop_global *pg, struct prop_local_percpu *pl)
-{
-	unsigned long period = 1UL << (pg->shift - 1);
-	unsigned long period_mask = ~(period - 1);
-	unsigned long global_period;
-	unsigned long flags;
-
-	global_period = percpu_counter_read(&pg->events);
-	global_period &= period_mask;
-
-	/*
-	 * Fast path - check if the local and global period count still match
-	 * outside of the lock.
-	 */
-	if (pl->period == global_period)
-		return;
-
-	raw_spin_lock_irqsave(&pl->lock, flags);
-	prop_adjust_shift(&pl->shift, &pl->period, pg->shift);
-
-	/*
-	 * For each missed period, we half the local counter.
-	 * basically:
-	 *   pl->events >> (global_period - pl->period);
-	 */
-	period = (global_period - pl->period) >> (pg->shift - 1);
-	if (period < BITS_PER_LONG) {
-		s64 val = percpu_counter_read(&pl->events);
-
-		if (val < (nr_cpu_ids * PROP_BATCH))
-			val = percpu_counter_sum(&pl->events);
-
-		__percpu_counter_add(&pl->events, -val + (val >> period),
-					PROP_BATCH);
-	} else
-		percpu_counter_set(&pl->events, 0);
-
-	pl->period = global_period;
-	raw_spin_unlock_irqrestore(&pl->lock, flags);
-}
-
-/*
- *   ++x_{j}, ++t
- */
-void __prop_inc_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl)
-{
-	struct prop_global *pg = prop_get_global(pd);
-
-	prop_norm_percpu(pg, pl);
-	__percpu_counter_add(&pl->events, 1, PROP_BATCH);
-	percpu_counter_add(&pg->events, 1);
-	prop_put_global(pd, pg);
-}
-
-/*
- * identical to __prop_inc_percpu, except that it limits this pl's fraction to
- * @frac/PROP_FRAC_BASE by ignoring events when this limit has been exceeded.
- */
-void __prop_inc_percpu_max(struct prop_descriptor *pd,
-			   struct prop_local_percpu *pl, long frac)
-{
-	struct prop_global *pg = prop_get_global(pd);
-
-	prop_norm_percpu(pg, pl);
-
-	if (unlikely(frac != PROP_FRAC_BASE)) {
-		unsigned long period_2 = 1UL << (pg->shift - 1);
-		unsigned long counter_mask = period_2 - 1;
-		unsigned long global_count;
-		long numerator, denominator;
-
-		numerator = percpu_counter_read_positive(&pl->events);
-		global_count = percpu_counter_read(&pg->events);
-		denominator = period_2 + (global_count & counter_mask);
-
-		if (numerator > ((denominator * frac) >> PROP_FRAC_SHIFT))
-			goto out_put;
-	}
-
-	percpu_counter_add(&pl->events, 1);
-	percpu_counter_add(&pg->events, 1);
-
-out_put:
-	prop_put_global(pd, pg);
-}
-
-/*
- * Obtain a fraction of this proportion
- *
- *   p_{j} = x_{j} / (period/2 + t % period/2)
- */
-void prop_fraction_percpu(struct prop_descriptor *pd,
-		struct prop_local_percpu *pl,
-		long *numerator, long *denominator)
-{
-	struct prop_global *pg = prop_get_global(pd);
-	unsigned long period_2 = 1UL << (pg->shift - 1);
-	unsigned long counter_mask = period_2 - 1;
-	unsigned long global_count;
-
-	prop_norm_percpu(pg, pl);
-	*numerator = percpu_counter_read_positive(&pl->events);
-
-	global_count = percpu_counter_read(&pg->events);
-	*denominator = period_2 + (global_count & counter_mask);
-
-	prop_put_global(pd, pg);
-}
-
-/*
- * SINGLE
- */
-
-int prop_local_init_single(struct prop_local_single *pl)
-{
-	raw_spin_lock_init(&pl->lock);
-	pl->shift = 0;
-	pl->period = 0;
-	pl->events = 0;
-	return 0;
-}
-
-void prop_local_destroy_single(struct prop_local_single *pl)
-{
-}
-
-/*
- * Catch up with missed period expirations.
- */
-static
-void prop_norm_single(struct prop_global *pg, struct prop_local_single *pl)
-{
-	unsigned long period = 1UL << (pg->shift - 1);
-	unsigned long period_mask = ~(period - 1);
-	unsigned long global_period;
-	unsigned long flags;
-
-	global_period = percpu_counter_read(&pg->events);
-	global_period &= period_mask;
-
-	/*
-	 * Fast path - check if the local and global period count still match
-	 * outside of the lock.
-	 */
-	if (pl->period == global_period)
-		return;
-
-	raw_spin_lock_irqsave(&pl->lock, flags);
-	prop_adjust_shift(&pl->shift, &pl->period, pg->shift);
-	/*
-	 * For each missed period, we half the local counter.
-	 */
-	period = (global_period - pl->period) >> (pg->shift - 1);
-	if (likely(period < BITS_PER_LONG))
-		pl->events >>= period;
-	else
-		pl->events = 0;
-	pl->period = global_period;
-	raw_spin_unlock_irqrestore(&pl->lock, flags);
-}
-
-/*
- *   ++x_{j}, ++t
- */
-void __prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl)
-{
-	struct prop_global *pg = prop_get_global(pd);
-
-	prop_norm_single(pg, pl);
-	pl->events++;
-	percpu_counter_add(&pg->events, 1);
-	prop_put_global(pd, pg);
-}
-
-/*
- * Obtain a fraction of this proportion
- *
- *   p_{j} = x_{j} / (period/2 + t % period/2)
- */
-void prop_fraction_single(struct prop_descriptor *pd,
-	       	struct prop_local_single *pl,
-		long *numerator, long *denominator)
-{
-	struct prop_global *pg = prop_get_global(pd);
-	unsigned long period_2 = 1UL << (pg->shift - 1);
-	unsigned long counter_mask = period_2 - 1;
-	unsigned long global_count;
-
-	prop_norm_single(pg, pl);
-	*numerator = pl->events;
-
-	global_count = percpu_counter_read(&pg->events);
-	*denominator = period_2 + (global_count & counter_mask);
-
-	prop_put_global(pd, pg);
-}
-- 
2.1.4