[Qemu-devel] [PATCH 37/47] add hierarchical bitmap data type and test cases

[Paolo Bonzini <pbonzini@redhat.com>]

HBitmaps provide 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.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hbitmap.c            |  394 ++++++++++++++++++++++++++++++++++++++++++++++++++
 hbitmap.h            |   51 +++++++
 tests/Makefile       |    2 +
 tests/test-hbitmap.c |  384 ++++++++++++++++++++++++++++++++++++++++++++++++
 trace-events         |    5 +
 5 files changed, 836 insertions(+)
 create mode 100644 hbitmap.c
 create mode 100644 hbitmap.h
 create mode 100644 tests/test-hbitmap.c

diff --git a/hbitmap.c b/hbitmap.c
new file mode 100644
index 0000000..cf14751
--- /dev/null
+++ b/hbitmap.c
@@ -0,0 +1,394 @@
+/*
+ * 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 "osdep.h"
+#include "hbitmap.h"
+#include "host-utils.h"
+#include "trace.h"
+#include <string.h>
+#include <glib.h>
+#include <assert.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.  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 amonut of bits.
+     * 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
+     */
+    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.
+     */
+    unsigned long *levels[HBITMAP_LEVELS];
+};
+
+static int64_t hbi_next_internal(HBitmapIter *hbi)
+{
+    unsigned long cur = hbi->cur[HBITMAP_LEVELS - 1];
+    size_t pos = hbi->pos;
+
+    if (cur == 0) {
+        HBitmap *hb = hbi->hb;
+        int i = HBITMAP_LEVELS - 1;
+
+        do {
+            cur = hbi->cur[--i];
+            pos >>= BITS_PER_LEVEL;
+        } while (cur == 0);
+
+        /* Check for end of iteration.  We only use up to
+         * BITS_PER_LEVEL bits (actually less) in the level 0 bitmap,
+         * and a sentinel is placed in hbitmap_alloc that ends the
+         * above loop.
+         */
+
+        if (i == 0 && (cur & (BITS_PER_LONG - 1)) == 0) {
+            return -1;
+        }
+        for (; i < HBITMAP_LEVELS - 1; i++) {
+            /* Find least significant set bit in the word, use them
+             * to add back shifted out bits to pos.
+             */
+            pos = (pos << BITS_PER_LEVEL) + ffsl(cur) - 1;
+            hbi->cur[i] = cur & (cur - 1);
+
+            /* Set up next level for iteration.  */
+            cur = hb->levels[i + 1][pos];
+        }
+
+        hbi->pos = pos;
+        hbi->cur[HBITMAP_LEVELS - 1] = cur & (cur - 1);
+    } else {
+        hbi->cur[HBITMAP_LEVELS - 1] &= cur - 1;
+    }
+    return ((uint64_t)pos << BITS_PER_LEVEL) + ffsl(cur) - 1;
+}
+
+static inline int popcountl(unsigned long l)
+{
+    return BITS_PER_LONG == 32 ? ctpop32(l) : ctpop64(l);
+}
+
+static int hbi_count_towards(HBitmapIter *hbi, uint64_t last)
+{
+    uint64_t next = hbi_next_internal(hbi);
+    int n;
+
+    /* Take it easy with the last few bits.  */
+    if (next >= (last & -BITS_PER_LONG)) {
+        return (next > last ? 0 : 1);
+    }
+
+    /* Process one word at a time, hbi_next_internal takes
+     * care of skipping large all-zero blocks.  Sum one to
+     * account for the value that was returned by next.
+     */
+    n = popcountl(hbi->cur[HBITMAP_LEVELS - 1]) + 1;
+    hbi->cur[HBITMAP_LEVELS - 1] = 0;
+    return n;
+}
+
+int64_t hbitmap_iter_next(HBitmapIter *hbi)
+{
+    int64_t next = hbi_next_internal(hbi);
+    trace_hbitmap_iter_next(hbi->hb, hbi, next << hbi->granularity, next);
+
+    return next << hbi->granularity;
+}
+
+void hbitmap_iter_init(HBitmapIter *hbi, HBitmap *hb, uint64_t first)
+{
+    int i, bit;
+    size_t pos;
+
+    hbi->hb = hb;
+    pos = first;
+    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);
+        }
+    }
+
+    hbi->pos = first >> BITS_PER_LEVEL;
+    hbi->granularity = hb->granularity;
+}
+
+bool hbitmap_empty(HBitmap *hb)
+{
+    return hb->count == 0;
+}
+
+uint64_t hbitmap_count(HBitmap *hb)
+{
+    return hb->count << hb->granularity;
+}
+
+/* Count the number of set bits between start and end, not accounting for
+ * the granularity.
+ */
+static int hb_count_between(HBitmap *hb, uint64_t start, uint64_t end)
+{
+    HBitmapIter hbi;
+    uint64_t count = 0, more;
+
+    hbitmap_iter_init(&hbi, hb, start);
+    do {
+        more = hbi_count_towards(&hbi, end);
+        count += more;
+    } while (more > 0);
+    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 end)
+{
+    unsigned long mask;
+    bool changed;
+
+    assert((end & -BITS_PER_LONG) == (start & -BITS_PER_LONG));
+
+    mask = 2UL << (end & (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 end)
+{
+    size_t pos = start >> BITS_PER_LEVEL;
+    size_t endpos = end >> BITS_PER_LEVEL;
+    bool changed = false;
+    size_t i;
+
+    i = pos;
+    if (i < endpos) {
+        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 == endpos) {
+                break;
+            }
+            changed |= (hb->levels[level][i] == 0);
+            hb->levels[level][i] = ~0UL;
+        }
+    }
+    changed |= hb_set_elem(&hb->levels[level][i], start, end);
+
+    /* If there was any change in this layer, we may have to update
+     * the one above.
+     */
+    if (level > 0 && changed) {
+        return hb_set_between(hb, level - 1, pos, endpos);
+    }
+}
+
+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 end)
+{
+    unsigned long mask;
+    bool blanked;
+
+    assert((end & -BITS_PER_LONG) == (start & -BITS_PER_LONG));
+
+    mask = 2UL << (end & (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 end)
+{
+    size_t pos = start >> BITS_PER_LEVEL;
+    size_t endpos = end >> BITS_PER_LEVEL;
+    bool changed = false;
+    size_t i;
+
+    i = pos;
+    if (i < endpos) {
+        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 == endpos) {
+                break;
+            }
+            changed |= (hb->levels[level][i] != 0);
+            hb->levels[level][i] = 0UL;
+        }
+    }
+
+    /* Same as above, this time for endpos.  */
+    if (hb_reset_elem(&hb->levels[level][i], start, end)) {
+        changed = true;
+    } else {
+        endpos--;
+    }
+
+    if (level > 0 && changed) {
+        return hb_reset_between(hb, level - 1, pos, endpos);
+    }
+}
+
+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(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)
+{
+    int 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));
+    int 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));
+    }
+
+    /* Add a sentinel in the level 0 bitmap.  We only use up to
+     * BITS_PER_LEVEL bits in level 0, so it's safe.
+     */
+    assert(size == 1);
+    hb->levels[0][0] |= 1UL << (BITS_PER_LONG - 1);
+    return hb;
+}
diff --git a/hbitmap.h b/hbitmap.h
new file mode 100644
index 0000000..2b717b0
--- /dev/null
+++ b/hbitmap.h
@@ -0,0 +1,51 @@
+/*
+ * 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.
+ */
+
+#ifndef HBITMAP_H
+#define HBITMAP_H 1
+
+#include <limits.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include "bitops.h"
+
+typedef struct HBitmap HBitmap;
+typedef struct HBitmapIter HBitmapIter;
+
+#define BITS_PER_LEVEL         (BITS_PER_LONG == 32 ? 5 : 6)
+
+/* For 32-bit, the largest that fits in a 4 GiB address space.
+ * For 64-bit, the number of sectors in 1 PiB.  Good luck, in
+ * either case... :)
+ */
+#define HBITMAP_LOG_MAX_SIZE   (BITS_PER_LONG == 32 ? 34 : 41)
+
+/* Leave an extra bit for a sentinel.  */
+#define HBITMAP_LEVELS         ((HBITMAP_LOG_MAX_SIZE / BITS_PER_LEVEL) + 1)
+
+struct HBitmapIter {
+    HBitmap *hb;
+    size_t pos;
+    int granularity;
+    unsigned long cur[HBITMAP_LEVELS];
+};
+
+int64_t hbitmap_iter_next(HBitmapIter *hbi);
+void hbitmap_iter_init(HBitmapIter *hbi, HBitmap *hb, uint64_t first);
+bool hbitmap_empty(HBitmap *hb);
+uint64_t hbitmap_count(HBitmap *hb);
+void hbitmap_set(HBitmap *hb, uint64_t start, uint64_t count);
+void hbitmap_reset(HBitmap *hb, uint64_t start, uint64_t count);
+bool hbitmap_get(HBitmap *hb, uint64_t item);
+void hbitmap_free(HBitmap *hb);
+HBitmap *hbitmap_alloc(uint64_t size, int granularity);
+
+#endif
diff --git a/tests/Makefile b/tests/Makefile
index 9675ba7..7e3bfed 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -15,6 +15,7 @@ check-unit-y += tests/test-string-output-visitor$(EXESUF)
 check-unit-y += tests/test-coroutine$(EXESUF)
 check-unit-y += tests/test-visitor-serialization$(EXESUF)
 check-unit-y += tests/test-iov$(EXESUF)
+check-unit-y += tests/test-hbitmap$(EXESUF)
 
 check-block-$(CONFIG_POSIX) += tests/qemu-iotests-quick.sh
 
@@ -50,6 +51,7 @@ tests/check-qfloat$(EXESUF): tests/check-qfloat.o qfloat.o $(tools-obj-y)
 tests/check-qjson$(EXESUF): tests/check-qjson.o $(qobject-obj-y) $(tools-obj-y)
 tests/test-coroutine$(EXESUF): tests/test-coroutine.o $(coroutine-obj-y) $(tools-obj-y)
 tests/test-iov$(EXESUF): tests/test-iov.o iov.o
+tests/test-hbitmap$(EXESUF): tests/test-hbitmap.o hbitmap.o $(trace-obj-y)
 
 tests/test-qapi-types.c tests/test-qapi-types.h :\
 $(SRC_PATH)/qapi-schema-test.json $(SRC_PATH)/scripts/qapi-types.py
diff --git a/tests/test-hbitmap.c b/tests/test-hbitmap.c
new file mode 100644
index 0000000..8a9b497
--- /dev/null
+++ b/tests/test-hbitmap.c
@@ -0,0 +1,384 @@
+/*
+ * Hierarchical bitmap unit-tests.
+ *
+ * Copyright (C) 2012 Red Hat Inc.
+ *
+ * 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 <glib.h>
+#include <stdarg.h>
+#include "hbitmap.h"
+
+#define LOG_BITS_PER_LONG          (BITS_PER_LONG == 32 ? 5 : 6)
+
+#define L1                         BITS_PER_LONG
+#define L2                         (BITS_PER_LONG * L1)
+#define L3                         (BITS_PER_LONG * L2)
+
+typedef struct TestHBitmapData {
+    HBitmap       *hb;
+    unsigned long *bits;
+    size_t         size;
+    int            granularity;
+} TestHBitmapData;
+
+
+/* Check that the HBitmap and the shadow bitmap contain the same data,
+ * ignoring the same "first" bits.
+ */
+static void hbitmap_test_check(TestHBitmapData *data,
+                               uint64_t first)
+{
+    uint64_t count = 0;
+    size_t pos;
+    int bit;
+    HBitmapIter hbi;
+    int64_t next;
+
+    hbitmap_iter_init(&hbi, data->hb, first);
+
+    for (;;) {
+        next = hbitmap_iter_next(&hbi);
+        if (next < 0) {
+            next = data->size;
+        }
+
+        while (first < next) {
+            pos = first >> LOG_BITS_PER_LONG;
+            bit = first & (BITS_PER_LONG - 1);
+            first++;
+            g_assert_cmpint(data->bits[pos] & (1UL << bit), ==, 0);
+        }
+
+        if (next == data->size) {
+            break;
+        }
+
+        pos = first >> LOG_BITS_PER_LONG;
+        bit = first & (BITS_PER_LONG - 1);
+        first++;
+        count++;
+        g_assert_cmpint(data->bits[pos] & (1UL << bit), !=, 0);
+    }
+
+    if (first == 0) {
+        g_assert_cmpint(count * data->granularity, ==, hbitmap_count(data->hb));
+    }
+}
+
+/* This is provided instead of a test setup function so that the sizes
+   are kept in the test functions (and not in main()) */
+static void hbitmap_test_init(TestHBitmapData *data,
+                              uint64_t size, int granularity)
+{
+    size_t n;
+    data->hb = hbitmap_alloc(size, granularity);
+
+    n = (size + BITS_PER_LONG - 1) / BITS_PER_LONG;
+    if (n == 0) {
+        n = 1;
+    }
+    data->bits = g_new0(unsigned long, n);
+    data->size = size;
+    data->granularity = granularity;
+    hbitmap_test_check(data, 0);
+}
+
+static void hbitmap_test_teardown(TestHBitmapData *data,
+                                  const void *unused)
+{
+    if (data->hb) {
+        hbitmap_free(data->hb);
+        data->hb = NULL;
+    }
+    if (data->bits) {
+        g_free(data->bits);
+        data->bits = NULL;
+    }
+}
+
+/* Set a range in the HBitmap and in the shadow "simple" bitmap.
+ * The two bitmaps are then tested against each other.
+ */
+static void hbitmap_test_set(TestHBitmapData *data,
+                             uint64_t first, uint64_t count)
+{
+    hbitmap_set(data->hb, first, count);
+    while (count-- != 0) {
+        size_t pos = first >> LOG_BITS_PER_LONG;
+        int bit = first & (BITS_PER_LONG - 1);
+        first++;
+
+        data->bits[pos] |= 1UL << bit;
+    }
+
+    if (data->granularity == 0) {
+        hbitmap_test_check(data, 0);
+    }
+}
+
+/* Reset a range in the HBitmap and in the shadow "simple" bitmap.
+ */
+static void hbitmap_test_reset(TestHBitmapData *data,
+                               uint64_t first, uint64_t count)
+{
+    hbitmap_reset(data->hb, first, count);
+    while (count-- != 0) {
+        size_t pos = first >> LOG_BITS_PER_LONG;
+        int bit = first & (BITS_PER_LONG - 1);
+        first++;
+
+        data->bits[pos] &= ~(1UL << bit);
+    }
+
+    if (data->granularity == 0) {
+        hbitmap_test_check(data, 0);
+    }
+}
+
+static void hbitmap_test_check_get(TestHBitmapData *data)
+{
+    uint64_t count = 0;
+    uint64_t i;
+
+    for (i = 0; i < data->size; i++) {
+        size_t pos = i >> LOG_BITS_PER_LONG;
+        int bit = i & (BITS_PER_LONG - 1);
+        unsigned long val = data->bits[pos] & (1UL << bit);
+        count += hbitmap_get(data->hb, i);
+        g_assert_cmpint(hbitmap_get(data->hb, i), ==, val != 0);
+    }
+    g_assert_cmpint(count, ==, hbitmap_count(data->hb));
+}
+
+static void test_hbitmap_zero(TestHBitmapData *data,
+                               const void *unused)
+{
+    hbitmap_test_init(data, 0, 0);
+}
+
+static void test_hbitmap_unaligned(TestHBitmapData *data,
+                                   const void *unused)
+{
+    hbitmap_test_init(data, L3 + 23, 0);
+    hbitmap_test_set(data, 0, 1);
+    hbitmap_test_set(data, L3 + 22, 1);
+}
+
+static void test_hbitmap_iter_empty(TestHBitmapData *data,
+                                    const void *unused)
+{
+    hbitmap_test_init(data, L1, 0);
+}
+
+static void test_hbitmap_iter_partial(TestHBitmapData *data,
+                                      const void *unused)
+{
+    hbitmap_test_init(data, L3, 0);
+    hbitmap_test_set(data, 0, L3);
+    hbitmap_test_check(data, 1);
+    hbitmap_test_check(data, L1 - 1);
+    hbitmap_test_check(data, L1);
+    hbitmap_test_check(data, L1 * 2 - 1);
+    hbitmap_test_check(data, L2 - 1);
+    hbitmap_test_check(data, L2);
+    hbitmap_test_check(data, L2 + 1);
+    hbitmap_test_check(data, L2 + L1);
+    hbitmap_test_check(data, L2 + L1 * 2 - 1);
+    hbitmap_test_check(data, L2 * 2 - 1);
+    hbitmap_test_check(data, L2 * 2);
+    hbitmap_test_check(data, L2 * 2 + 1);
+    hbitmap_test_check(data, L2 * 2 + L1);
+    hbitmap_test_check(data, L2 * 2 + L1 * 2 - 1);
+    hbitmap_test_check(data, L3 / 2);
+}
+
+static void test_hbitmap_iter_past(TestHBitmapData *data,
+                                    const void *unused)
+{
+    hbitmap_test_init(data, L3, 0);
+    hbitmap_test_set(data, 0, L3);
+    hbitmap_test_check(data, L3);
+}
+
+static void test_hbitmap_set_all(TestHBitmapData *data,
+                                 const void *unused)
+{
+    hbitmap_test_init(data, L3, 0);
+    hbitmap_test_set(data, 0, L3);
+}
+
+static void test_hbitmap_get_all(TestHBitmapData *data,
+                                 const void *unused)
+{
+    hbitmap_test_init(data, L3, 0);
+    hbitmap_test_set(data, 0, L3);
+    hbitmap_test_check_get(data);
+}
+
+static void test_hbitmap_get_some(TestHBitmapData *data,
+                                  const void *unused)
+{
+    hbitmap_test_init(data, 2 * L2, 0);
+    hbitmap_test_set(data, 10, 1);
+    hbitmap_test_check_get(data);
+    hbitmap_test_set(data, L1 - 1, 1);
+    hbitmap_test_check_get(data);
+    hbitmap_test_set(data, L1, 1);
+    hbitmap_test_check_get(data);
+    hbitmap_test_set(data, L2 - 1, 1);
+    hbitmap_test_check_get(data);
+    hbitmap_test_set(data, L2, 1);
+    hbitmap_test_check_get(data);
+}
+
+static void test_hbitmap_set_one(TestHBitmapData *data,
+                                 const void *unused)
+{
+    hbitmap_test_init(data, 2 * L2, 0);
+    hbitmap_test_set(data, 10, 1);
+    hbitmap_test_set(data, L1 - 1, 1);
+    hbitmap_test_set(data, L1, 1);
+    hbitmap_test_set(data, L2 - 1, 1);
+    hbitmap_test_set(data, L2, 1);
+}
+
+static void test_hbitmap_set_two_elem(TestHBitmapData *data,
+                                      const void *unused)
+{
+    hbitmap_test_init(data, 2 * L2, 0);
+    hbitmap_test_set(data, L1 - 1, 2);
+    hbitmap_test_set(data, L1 * 2 - 1, 4);
+    hbitmap_test_set(data, L1 * 4, L1 + 1);
+    hbitmap_test_set(data, L1 * 8 - 1, L1 + 1);
+    hbitmap_test_set(data, L2 - 1, 2);
+    hbitmap_test_set(data, L2 + L1 - 1, 8);
+    hbitmap_test_set(data, L2 + L1 * 4, L1 + 1);
+    hbitmap_test_set(data, L2 + L1 * 8 - 1, L1 + 1);
+}
+
+static void test_hbitmap_set(TestHBitmapData *data,
+                             const void *unused)
+{
+    hbitmap_test_init(data, L3 * 2, 0);
+    hbitmap_test_set(data, L1 - 1, L1 + 2);
+    hbitmap_test_set(data, L1 * 3 - 1, L1 + 2);
+    hbitmap_test_set(data, L1 * 5, L1 * 2 + 1);
+    hbitmap_test_set(data, L1 * 8 - 1, L1 * 2 + 1);
+    hbitmap_test_set(data, L2 - 1, L1 + 2);
+    hbitmap_test_set(data, L2 + L1 * 2 - 1, L1 + 2);
+    hbitmap_test_set(data, L2 + L1 * 4, L1 * 2 + 1);
+    hbitmap_test_set(data, L2 + L1 * 7 - 1, L1 * 2 + 1);
+    hbitmap_test_set(data, L2 * 2 - 1, L3 * 2 - L2 * 2);
+}
+
+static void test_hbitmap_set_overlap(TestHBitmapData *data,
+                                     const void *unused)
+{
+    hbitmap_test_init(data, L3 * 2, 0);
+    hbitmap_test_set(data, L1 - 1, L1 + 2);
+    hbitmap_test_set(data, L1 * 2 - 1, L1 * 2 + 2);
+    hbitmap_test_set(data, 0, L1 * 3);
+    hbitmap_test_set(data, L1 * 8 - 1, L2);
+    hbitmap_test_set(data, L2, L1);
+    hbitmap_test_set(data, L2 - L1 - 1, L1 * 8 + 2);
+    hbitmap_test_set(data, L2, L3 - L2 + 1);
+    hbitmap_test_set(data, L3 - L1, L1 * 3);
+    hbitmap_test_set(data, L3 - 1, 3);
+    hbitmap_test_set(data, L3 - 1, L2);
+}
+
+static void test_hbitmap_reset_empty(TestHBitmapData *data,
+                                     const void *unused)
+{
+    hbitmap_test_init(data, L3, 0);
+    hbitmap_test_reset(data, 0, L3);
+}
+
+static void test_hbitmap_reset(TestHBitmapData *data,
+                               const void *unused)
+{
+    hbitmap_test_init(data, L3 * 2, 0);
+    hbitmap_test_set(data, L1 - 1, L1 + 2);
+    hbitmap_test_reset(data, L1 * 2 - 1, L1 * 2 + 2);
+    hbitmap_test_set(data, 0, L1 * 3);
+    hbitmap_test_reset(data, L1 * 8 - 1, L2);
+    hbitmap_test_set(data, L2, L1);
+    hbitmap_test_reset(data, L2 - L1 - 1, L1 * 8 + 2);
+    hbitmap_test_set(data, L2, L3 - L2 + 1);
+    hbitmap_test_reset(data, L3 - L1, L1 * 3);
+    hbitmap_test_set(data, L3 - 1, 3);
+    hbitmap_test_reset(data, L3 - 1, L2);
+    hbitmap_test_set(data, 0, L3 * 2);
+    hbitmap_test_reset(data, 0, L1);
+    hbitmap_test_reset(data, 0, L2);
+    hbitmap_test_reset(data, L3, L3);
+    hbitmap_test_set(data, L3 / 2, L3);
+}
+
+static void test_hbitmap_granularity(TestHBitmapData *data,
+                                     const void *unused)
+{
+    /* Note that hbitmap_test_check has to be invoked manually in this test.  */
+    hbitmap_test_init(data, L1, 1);
+    hbitmap_test_set(data, 0, 1);
+    hbitmap_test_check(data, 0);
+    hbitmap_test_set(data, 2, 1);
+    hbitmap_test_check(data, 0);
+    hbitmap_test_set(data, 0, 3);
+    g_assert_cmpint(hbitmap_count(data->hb), ==, 4);
+    hbitmap_test_reset(data, 0, 1);
+    g_assert_cmpint(hbitmap_count(data->hb), ==, 2);
+}
+
+static void test_hbitmap_iter_granularity(TestHBitmapData *data,
+                                          const void *unused)
+{
+    HBitmapIter hbi;
+
+    /* Note that hbitmap_test_check has to be invoked manually in this test.  */
+    hbitmap_test_init(data, 131072 << 7, 7);
+    hbitmap_iter_init(&hbi, data->hb, 0);
+    g_assert_cmpint(hbitmap_iter_next(&hbi), <, 0);
+    hbitmap_test_set(data, ((L2 + L1 + 1) << 7) + 8, 8);
+    hbitmap_iter_init(&hbi, data->hb, 0);
+    g_assert_cmpint(hbitmap_iter_next(&hbi), ==, (L2 + L1 + 1) << 7);
+}
+
+static void hbitmap_test_add(const char *testpath,
+                                   TestHBitmapData *data,
+                                   void (*test_func)(TestHBitmapData *data, const void *user_data))
+{
+    g_test_add(testpath, TestHBitmapData, data, NULL, test_func,
+               hbitmap_test_teardown);
+}
+
+int main(int argc, char **argv)
+{
+    TestHBitmapData hbitmap_data;
+
+    g_test_init(&argc, &argv, NULL);
+    hbitmap_test_add("/hbitmap/size/0", &hbitmap_data, test_hbitmap_zero);
+    hbitmap_test_add("/hbitmap/size/unaligned", &hbitmap_data, test_hbitmap_unaligned);
+    hbitmap_test_add("/hbitmap/iter/empty", &hbitmap_data, test_hbitmap_iter_empty);
+    hbitmap_test_add("/hbitmap/iter/past", &hbitmap_data, test_hbitmap_iter_past);
+    hbitmap_test_add("/hbitmap/iter/partial", &hbitmap_data, test_hbitmap_iter_partial);
+    hbitmap_test_add("/hbitmap/iter/granularity", &hbitmap_data, test_hbitmap_iter_granularity);
+    hbitmap_test_add("/hbitmap/get/all", &hbitmap_data, test_hbitmap_get_all);
+    hbitmap_test_add("/hbitmap/get/some", &hbitmap_data, test_hbitmap_get_some);
+    hbitmap_test_add("/hbitmap/set/all", &hbitmap_data, test_hbitmap_set_all);
+    hbitmap_test_add("/hbitmap/set/one", &hbitmap_data, test_hbitmap_set_one);
+    hbitmap_test_add("/hbitmap/set/two-elem", &hbitmap_data, test_hbitmap_set_two_elem);
+    hbitmap_test_add("/hbitmap/set/general", &hbitmap_data, test_hbitmap_set);
+    hbitmap_test_add("/hbitmap/set/overlap", &hbitmap_data, test_hbitmap_set_overlap);
+    hbitmap_test_add("/hbitmap/reset/empty", &hbitmap_data, test_hbitmap_reset_empty);
+    hbitmap_test_add("/hbitmap/reset/general", &hbitmap_data, test_hbitmap_reset);
+    hbitmap_test_add("/hbitmap/granularity", &hbitmap_data, test_hbitmap_granularity);
+    g_test_run();
+
+    return 0;
+}
diff --git a/trace-events b/trace-events
index ac58f3a..9313ae7 100644
--- a/trace-events
+++ b/trace-events
@@ -977,3 +977,8 @@ qxl_render_blit_guest_primary_initialized(void) ""
 qxl_render_blit(int32_t stride, int32_t left, int32_t right, int32_t top, int32_t bottom) "stride=%d [%d, %d, %d, %d]"
 qxl_render_guest_primary_resized(int32_t width, int32_t height, int32_t stride, int32_t bytes_pp, int32_t bits_pp) "%dx%d, stride %d, bpp %d, depth %d"
 qxl_render_update_area_done(void *cookie) "%p"
+
+# hbitmap.c
+hbitmap_iter_next(void *hb, void *hbi, int64_t item, int64_t bit) "hb %p hbi %p item %"PRId64" bit %"PRId64
+hbitmap_reset(void *hb, uint64_t start, uint64_t count, uint64_t sbit, uint64_t ebit) "hb %p items %"PRIu64",%"PRIu64" bits %"PRIu64"..%"PRIu64
+hbitmap_set(void *hb, uint64_t start, uint64_t count, uint64_t sbit, uint64_t ebit) "hb %p items %"PRIu64",%"PRIu64" bits %"PRIu64"..%"PRIu64
-- 
1.7.10.4