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authorAnand Avati <avati@redhat.com>2013-03-06 01:11:59 -0800
committerAnand Avati <avati@redhat.com>2013-09-03 11:25:33 -0700
commit0d60175bd684cf6a14f750579d82dbd1ba97fcbc (patch)
tree1571f530548196006526442f3fc027cb623bb6fa /contrib/qemu/util/hbitmap.c
parent7dbfbfd3694e02b90e8f3ce509f5279da1523a02 (diff)
contrib/qemu: Import qemu block source code
This qemu block format source code and its minimal dependency files will be used in the next patch to implement a qemu-block format translator. Change-Id: Ic87638972f7ea9b3df84d7a0539512a250c11c1c BUG: 986775 Signed-off-by: Anand Avati <avati@redhat.com> Reviewed-on: http://review.gluster.org/5366 Tested-by: Gluster Build System <jenkins@build.gluster.com> Reviewed-by: Brian Foster <bfoster@redhat.com>
Diffstat (limited to 'contrib/qemu/util/hbitmap.c')
-rw-r--r--contrib/qemu/util/hbitmap.c402
1 files changed, 402 insertions, 0 deletions
diff --git a/contrib/qemu/util/hbitmap.c b/contrib/qemu/util/hbitmap.c
new file mode 100644
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+++ b/contrib/qemu/util/hbitmap.c
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+/*
+ * 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 <string.h>
+#include <glib.h>
+#include <assert.h>
+#include "qemu/osdep.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];
+};
+
+static inline int popcountl(unsigned long l)
+{
+ return BITS_PER_LONG == 32 ? ctpop32(l) : ctpop64(l);
+}
+
+/* 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 += popcountl(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 += popcountl(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);
+}
+
+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_malloc0(sizeof (struct HBitmap));
+ 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->levels[i] = g_malloc0(size * sizeof(unsigned long));
+ }
+
+ /* 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;
+}