summaryrefslogtreecommitdiffstats
path: root/qemu/util/hbitmap.c
diff options
context:
space:
mode:
Diffstat (limited to 'qemu/util/hbitmap.c')
-rw-r--r--qemu/util/hbitmap.c493
1 files changed, 0 insertions, 493 deletions
diff --git a/qemu/util/hbitmap.c b/qemu/util/hbitmap.c
deleted file mode 100644
index b22b87d0a..000000000
--- a/qemu/util/hbitmap.c
+++ /dev/null
@@ -1,493 +0,0 @@
-/*
- * Hierarchical Bitmap Data Type
- *
- * Copyright Red Hat, Inc., 2012
- *
- * Author: Paolo Bonzini <pbonzini@redhat.com>
- *
- * This work is licensed under the terms of the GNU GPL, version 2 or
- * later. See the COPYING file in the top-level directory.
- */
-
-#include "qemu/osdep.h"
-#include <glib.h>
-#include "qemu/hbitmap.h"
-#include "qemu/host-utils.h"
-#include "trace.h"
-
-/* HBitmaps provides an array of bits. The bits are stored as usual in an
- * array of unsigned longs, but HBitmap is also optimized to provide fast
- * iteration over set bits; going from one bit to the next is O(logB n)
- * worst case, with B = sizeof(long) * CHAR_BIT: the result is low enough
- * that the number of levels is in fact fixed.
- *
- * In order to do this, it stacks multiple bitmaps with progressively coarser
- * granularity; in all levels except the last, bit N is set iff the N-th
- * unsigned long is nonzero in the immediately next level. When iteration
- * completes on the last level it can examine the 2nd-last level to quickly
- * skip entire words, and even do so recursively to skip blocks of 64 words or
- * powers thereof (32 on 32-bit machines).
- *
- * Given an index in the bitmap, it can be split in group of bits like
- * this (for the 64-bit case):
- *
- * bits 0-57 => word in the last bitmap | bits 58-63 => bit in the word
- * bits 0-51 => word in the 2nd-last bitmap | bits 52-57 => bit in the word
- * bits 0-45 => word in the 3rd-last bitmap | bits 46-51 => bit in the word
- *
- * So it is easy to move up simply by shifting the index right by
- * log2(BITS_PER_LONG) bits. To move down, you shift the index left
- * similarly, and add the word index within the group. Iteration uses
- * ffs (find first set bit) to find the next word to examine; this
- * operation can be done in constant time in most current architectures.
- *
- * Setting or clearing a range of m bits on all levels, the work to perform
- * is O(m + m/W + m/W^2 + ...), which is O(m) like on a regular bitmap.
- *
- * When iterating on a bitmap, each bit (on any level) is only visited
- * once. Hence, The total cost of visiting a bitmap with m bits in it is
- * the number of bits that are set in all bitmaps. Unless the bitmap is
- * extremely sparse, this is also O(m + m/W + m/W^2 + ...), so the amortized
- * cost of advancing from one bit to the next is usually constant (worst case
- * O(logB n) as in the non-amortized complexity).
- */
-
-struct HBitmap {
- /* Number of total bits in the bottom level. */
- uint64_t size;
-
- /* Number of set bits in the bottom level. */
- uint64_t count;
-
- /* A scaling factor. Given a granularity of G, each bit in the bitmap will
- * will actually represent a group of 2^G elements. Each operation on a
- * range of bits first rounds the bits to determine which group they land
- * in, and then affect the entire page; iteration will only visit the first
- * bit of each group. Here is an example of operations in a size-16,
- * granularity-1 HBitmap:
- *
- * initial state 00000000
- * set(start=0, count=9) 11111000 (iter: 0, 2, 4, 6, 8)
- * reset(start=1, count=3) 00111000 (iter: 4, 6, 8)
- * set(start=9, count=2) 00111100 (iter: 4, 6, 8, 10)
- * reset(start=5, count=5) 00000000
- *
- * From an implementation point of view, when setting or resetting bits,
- * the bitmap will scale bit numbers right by this amount of bits. When
- * iterating, the bitmap will scale bit numbers left by this amount of
- * bits.
- */
- int granularity;
-
- /* A number of progressively less coarse bitmaps (i.e. level 0 is the
- * coarsest). Each bit in level N represents a word in level N+1 that
- * has a set bit, except the last level where each bit represents the
- * actual bitmap.
- *
- * Note that all bitmaps have the same number of levels. Even a 1-bit
- * bitmap will still allocate HBITMAP_LEVELS arrays.
- */
- unsigned long *levels[HBITMAP_LEVELS];
-
- /* The length of each levels[] array. */
- uint64_t sizes[HBITMAP_LEVELS];
-};
-
-/* Advance hbi to the next nonzero word and return it. hbi->pos
- * is updated. Returns zero if we reach the end of the bitmap.
- */
-unsigned long hbitmap_iter_skip_words(HBitmapIter *hbi)
-{
- size_t pos = hbi->pos;
- const HBitmap *hb = hbi->hb;
- unsigned i = HBITMAP_LEVELS - 1;
-
- unsigned long cur;
- do {
- cur = hbi->cur[--i];
- pos >>= BITS_PER_LEVEL;
- } while (cur == 0);
-
- /* Check for end of iteration. We always use fewer than BITS_PER_LONG
- * bits in the level 0 bitmap; thus we can repurpose the most significant
- * bit as a sentinel. The sentinel is set in hbitmap_alloc and ensures
- * that the above loop ends even without an explicit check on i.
- */
-
- if (i == 0 && cur == (1UL << (BITS_PER_LONG - 1))) {
- return 0;
- }
- for (; i < HBITMAP_LEVELS - 1; i++) {
- /* Shift back pos to the left, matching the right shifts above.
- * The index of this word's least significant set bit provides
- * the low-order bits.
- */
- assert(cur);
- pos = (pos << BITS_PER_LEVEL) + ctzl(cur);
- hbi->cur[i] = cur & (cur - 1);
-
- /* Set up next level for iteration. */
- cur = hb->levels[i + 1][pos];
- }
-
- hbi->pos = pos;
- trace_hbitmap_iter_skip_words(hbi->hb, hbi, pos, cur);
-
- assert(cur);
- return cur;
-}
-
-void hbitmap_iter_init(HBitmapIter *hbi, const HBitmap *hb, uint64_t first)
-{
- unsigned i, bit;
- uint64_t pos;
-
- hbi->hb = hb;
- pos = first >> hb->granularity;
- assert(pos < hb->size);
- hbi->pos = pos >> BITS_PER_LEVEL;
- hbi->granularity = hb->granularity;
-
- for (i = HBITMAP_LEVELS; i-- > 0; ) {
- bit = pos & (BITS_PER_LONG - 1);
- pos >>= BITS_PER_LEVEL;
-
- /* Drop bits representing items before first. */
- hbi->cur[i] = hb->levels[i][pos] & ~((1UL << bit) - 1);
-
- /* We have already added level i+1, so the lowest set bit has
- * been processed. Clear it.
- */
- if (i != HBITMAP_LEVELS - 1) {
- hbi->cur[i] &= ~(1UL << bit);
- }
- }
-}
-
-bool hbitmap_empty(const HBitmap *hb)
-{
- return hb->count == 0;
-}
-
-int hbitmap_granularity(const HBitmap *hb)
-{
- return hb->granularity;
-}
-
-uint64_t hbitmap_count(const HBitmap *hb)
-{
- return hb->count << hb->granularity;
-}
-
-/* Count the number of set bits between start and end, not accounting for
- * the granularity. Also an example of how to use hbitmap_iter_next_word.
- */
-static uint64_t hb_count_between(HBitmap *hb, uint64_t start, uint64_t last)
-{
- HBitmapIter hbi;
- uint64_t count = 0;
- uint64_t end = last + 1;
- unsigned long cur;
- size_t pos;
-
- hbitmap_iter_init(&hbi, hb, start << hb->granularity);
- for (;;) {
- pos = hbitmap_iter_next_word(&hbi, &cur);
- if (pos >= (end >> BITS_PER_LEVEL)) {
- break;
- }
- count += ctpopl(cur);
- }
-
- if (pos == (end >> BITS_PER_LEVEL)) {
- /* Drop bits representing the END-th and subsequent items. */
- int bit = end & (BITS_PER_LONG - 1);
- cur &= (1UL << bit) - 1;
- count += ctpopl(cur);
- }
-
- return count;
-}
-
-/* Setting starts at the last layer and propagates up if an element
- * changes from zero to non-zero.
- */
-static inline bool hb_set_elem(unsigned long *elem, uint64_t start, uint64_t last)
-{
- unsigned long mask;
- bool changed;
-
- assert((last >> BITS_PER_LEVEL) == (start >> BITS_PER_LEVEL));
- assert(start <= last);
-
- mask = 2UL << (last & (BITS_PER_LONG - 1));
- mask -= 1UL << (start & (BITS_PER_LONG - 1));
- changed = (*elem == 0);
- *elem |= mask;
- return changed;
-}
-
-/* The recursive workhorse (the depth is limited to HBITMAP_LEVELS)... */
-static void hb_set_between(HBitmap *hb, int level, uint64_t start, uint64_t last)
-{
- size_t pos = start >> BITS_PER_LEVEL;
- size_t lastpos = last >> BITS_PER_LEVEL;
- bool changed = false;
- size_t i;
-
- i = pos;
- if (i < lastpos) {
- uint64_t next = (start | (BITS_PER_LONG - 1)) + 1;
- changed |= hb_set_elem(&hb->levels[level][i], start, next - 1);
- for (;;) {
- start = next;
- next += BITS_PER_LONG;
- if (++i == lastpos) {
- break;
- }
- changed |= (hb->levels[level][i] == 0);
- hb->levels[level][i] = ~0UL;
- }
- }
- changed |= hb_set_elem(&hb->levels[level][i], start, last);
-
- /* If there was any change in this layer, we may have to update
- * the one above.
- */
- if (level > 0 && changed) {
- hb_set_between(hb, level - 1, pos, lastpos);
- }
-}
-
-void hbitmap_set(HBitmap *hb, uint64_t start, uint64_t count)
-{
- /* Compute range in the last layer. */
- uint64_t last = start + count - 1;
-
- trace_hbitmap_set(hb, start, count,
- start >> hb->granularity, last >> hb->granularity);
-
- start >>= hb->granularity;
- last >>= hb->granularity;
- count = last - start + 1;
-
- hb->count += count - hb_count_between(hb, start, last);
- hb_set_between(hb, HBITMAP_LEVELS - 1, start, last);
-}
-
-/* Resetting works the other way round: propagate up if the new
- * value is zero.
- */
-static inline bool hb_reset_elem(unsigned long *elem, uint64_t start, uint64_t last)
-{
- unsigned long mask;
- bool blanked;
-
- assert((last >> BITS_PER_LEVEL) == (start >> BITS_PER_LEVEL));
- assert(start <= last);
-
- mask = 2UL << (last & (BITS_PER_LONG - 1));
- mask -= 1UL << (start & (BITS_PER_LONG - 1));
- blanked = *elem != 0 && ((*elem & ~mask) == 0);
- *elem &= ~mask;
- return blanked;
-}
-
-/* The recursive workhorse (the depth is limited to HBITMAP_LEVELS)... */
-static void hb_reset_between(HBitmap *hb, int level, uint64_t start, uint64_t last)
-{
- size_t pos = start >> BITS_PER_LEVEL;
- size_t lastpos = last >> BITS_PER_LEVEL;
- bool changed = false;
- size_t i;
-
- i = pos;
- if (i < lastpos) {
- uint64_t next = (start | (BITS_PER_LONG - 1)) + 1;
-
- /* Here we need a more complex test than when setting bits. Even if
- * something was changed, we must not blank bits in the upper level
- * unless the lower-level word became entirely zero. So, remove pos
- * from the upper-level range if bits remain set.
- */
- if (hb_reset_elem(&hb->levels[level][i], start, next - 1)) {
- changed = true;
- } else {
- pos++;
- }
-
- for (;;) {
- start = next;
- next += BITS_PER_LONG;
- if (++i == lastpos) {
- break;
- }
- changed |= (hb->levels[level][i] != 0);
- hb->levels[level][i] = 0UL;
- }
- }
-
- /* Same as above, this time for lastpos. */
- if (hb_reset_elem(&hb->levels[level][i], start, last)) {
- changed = true;
- } else {
- lastpos--;
- }
-
- if (level > 0 && changed) {
- hb_reset_between(hb, level - 1, pos, lastpos);
- }
-}
-
-void hbitmap_reset(HBitmap *hb, uint64_t start, uint64_t count)
-{
- /* Compute range in the last layer. */
- uint64_t last = start + count - 1;
-
- trace_hbitmap_reset(hb, start, count,
- start >> hb->granularity, last >> hb->granularity);
-
- start >>= hb->granularity;
- last >>= hb->granularity;
-
- hb->count -= hb_count_between(hb, start, last);
- hb_reset_between(hb, HBITMAP_LEVELS - 1, start, last);
-}
-
-void hbitmap_reset_all(HBitmap *hb)
-{
- unsigned int i;
-
- /* Same as hbitmap_alloc() except for memset() instead of malloc() */
- for (i = HBITMAP_LEVELS; --i >= 1; ) {
- memset(hb->levels[i], 0, hb->sizes[i] * sizeof(unsigned long));
- }
-
- hb->levels[0][0] = 1UL << (BITS_PER_LONG - 1);
- hb->count = 0;
-}
-
-bool hbitmap_get(const HBitmap *hb, uint64_t item)
-{
- /* Compute position and bit in the last layer. */
- uint64_t pos = item >> hb->granularity;
- unsigned long bit = 1UL << (pos & (BITS_PER_LONG - 1));
-
- return (hb->levels[HBITMAP_LEVELS - 1][pos >> BITS_PER_LEVEL] & bit) != 0;
-}
-
-void hbitmap_free(HBitmap *hb)
-{
- unsigned i;
- for (i = HBITMAP_LEVELS; i-- > 0; ) {
- g_free(hb->levels[i]);
- }
- g_free(hb);
-}
-
-HBitmap *hbitmap_alloc(uint64_t size, int granularity)
-{
- HBitmap *hb = g_new0(struct HBitmap, 1);
- unsigned i;
-
- assert(granularity >= 0 && granularity < 64);
- size = (size + (1ULL << granularity) - 1) >> granularity;
- assert(size <= ((uint64_t)1 << HBITMAP_LOG_MAX_SIZE));
-
- hb->size = size;
- hb->granularity = granularity;
- for (i = HBITMAP_LEVELS; i-- > 0; ) {
- size = MAX((size + BITS_PER_LONG - 1) >> BITS_PER_LEVEL, 1);
- hb->sizes[i] = size;
- hb->levels[i] = g_new0(unsigned long, size);
- }
-
- /* We necessarily have free bits in level 0 due to the definition
- * of HBITMAP_LEVELS, so use one for a sentinel. This speeds up
- * hbitmap_iter_skip_words.
- */
- assert(size == 1);
- hb->levels[0][0] |= 1UL << (BITS_PER_LONG - 1);
- return hb;
-}
-
-void hbitmap_truncate(HBitmap *hb, uint64_t size)
-{
- bool shrink;
- unsigned i;
- uint64_t num_elements = size;
- uint64_t old;
-
- /* Size comes in as logical elements, adjust for granularity. */
- size = (size + (1ULL << hb->granularity) - 1) >> hb->granularity;
- assert(size <= ((uint64_t)1 << HBITMAP_LOG_MAX_SIZE));
- shrink = size < hb->size;
-
- /* bit sizes are identical; nothing to do. */
- if (size == hb->size) {
- return;
- }
-
- /* If we're losing bits, let's clear those bits before we invalidate all of
- * our invariants. This helps keep the bitcount consistent, and will prevent
- * us from carrying around garbage bits beyond the end of the map.
- */
- if (shrink) {
- /* Don't clear partial granularity groups;
- * start at the first full one. */
- uint64_t start = QEMU_ALIGN_UP(num_elements, 1 << hb->granularity);
- uint64_t fix_count = (hb->size << hb->granularity) - start;
-
- assert(fix_count);
- hbitmap_reset(hb, start, fix_count);
- }
-
- hb->size = size;
- for (i = HBITMAP_LEVELS; i-- > 0; ) {
- size = MAX(BITS_TO_LONGS(size), 1);
- if (hb->sizes[i] == size) {
- break;
- }
- old = hb->sizes[i];
- hb->sizes[i] = size;
- hb->levels[i] = g_realloc(hb->levels[i], size * sizeof(unsigned long));
- if (!shrink) {
- memset(&hb->levels[i][old], 0x00,
- (size - old) * sizeof(*hb->levels[i]));
- }
- }
-}
-
-
-/**
- * Given HBitmaps A and B, let A := A (BITOR) B.
- * Bitmap B will not be modified.
- *
- * @return true if the merge was successful,
- * false if it was not attempted.
- */
-bool hbitmap_merge(HBitmap *a, const HBitmap *b)
-{
- int i;
- uint64_t j;
-
- if ((a->size != b->size) || (a->granularity != b->granularity)) {
- return false;
- }
-
- if (hbitmap_count(b) == 0) {
- return true;
- }
-
- /* This merge is O(size), as BITS_PER_LONG and HBITMAP_LEVELS are constant.
- * It may be possible to improve running times for sparsely populated maps
- * by using hbitmap_iter_next, but this is suboptimal for dense maps.
- */
- for (i = HBITMAP_LEVELS - 1; i >= 0; i--) {
- for (j = 0; j < a->sizes[i]; j++) {
- a->levels[i][j] |= b->levels[i][j];
- }
- }
-
- return true;
-}