lib/bitmap: Faster bitmap functions.

Replace bitwise loops with a single operation, inline all bitmap
functions.  Inlining allows the compiler to remove unnecessary code
due to some parameters being compile-time constants.

Before:

$ tests/ovstest test-bitmap benchmark 1000000
bitmap equal:    341 ms
bitmap scan:   8089 ms

After:

$ tests/ovstest test-bitmap benchmark 1000000
bitmap equal:    152 ms
bitmap scan:    146 ms

Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Co-authored-by: Kmindg <kmindg@gmail.com>
Acked-by: Ben Pfaff <blp@nicira.com>

lib/automake.mk

@@ -23,7 +23,6 @@ lib_libopenvswitch_la_SOURCES = \
 	lib/backtrace.h \
 	lib/bfd.c \
 	lib/bfd.h \
-	lib/bitmap.c \
 	lib/bitmap.h \
 	lib/bundle.c \
 	lib/bundle.h \

lib/bitmap.c

@@ -1,155 +0,0 @@
-/*
- * Copyright (c) 2008, 2009, 2011, 2014 Nicira, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at:
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include <config.h>
-#include "bitmap.h"
-#include <string.h>
-#include "util.h"
-
-/* Allocates and returns a bitmap initialized to all-1-bits. */
-unsigned long *
-bitmap_allocate1(size_t n_bits)
-{
-    size_t n_bytes = bitmap_n_bytes(n_bits);
-    size_t n_longs = bitmap_n_longs(n_bits);
-    size_t r_bits = n_bits % BITMAP_ULONG_BITS;
-    unsigned long *bitmap;
-
-    /* Allocate and initialize most of the bitmap. */
-    bitmap = xmalloc(n_bytes);
-    memset(bitmap, 0xff, n_bytes);
-
-    /* Ensure that the last "unsigned long" in the bitmap only has as many
-     * 1-bits as there actually should be. */
-    if (r_bits) {
-        bitmap[n_longs - 1] = (1UL << r_bits) - 1;
-    }
-
-    return bitmap;
-}
-
-/* Sets 'count' consecutive bits in 'bitmap', starting at bit offset 'start',
- * to 'value'. */
-void
-bitmap_set_multiple(unsigned long *bitmap, size_t start, size_t count,
-                    bool value)
-{
-    for (; count && start % BITMAP_ULONG_BITS; count--) {
-        bitmap_set(bitmap, start++, value);
-    }
-    for (; count >= BITMAP_ULONG_BITS; count -= BITMAP_ULONG_BITS) {
-        *bitmap_unit__(bitmap, start) = -(unsigned long) value;
-        start += BITMAP_ULONG_BITS;
-    }
-    for (; count; count--) {
-        bitmap_set(bitmap, start++, value);
-    }
-}
-
-/* Compares the 'n' bits in bitmaps 'a' and 'b'.  Returns true if all bits are
- * equal, false otherwise. */
-bool
-bitmap_equal(const unsigned long *a, const unsigned long *b, size_t n)
-{
-    size_t i;
-
-    if (memcmp(a, b, n / BITMAP_ULONG_BITS * sizeof(unsigned long))) {
-        return false;
-    }
-    for (i = ROUND_DOWN(n, BITMAP_ULONG_BITS); i < n; i++) {
-        if (bitmap_is_set(a, i) != bitmap_is_set(b, i)) {
-            return false;
-        }
-    }
-    return true;
-}
-
-/* Scans 'bitmap' from bit offset 'start' to 'end', excluding 'end' itself.
- * Returns the bit offset of the lowest-numbered bit set to 'target', or 'end'
- * if all of the bits are set to '!target'. */
-size_t
-bitmap_scan(const unsigned long int *bitmap, bool target,
-            size_t start, size_t end)
-{
-    /* XXX slow */
-    size_t i;
-
-    for (i = start; i < end; i++) {
-        if (bitmap_is_set(bitmap, i) == target) {
-            break;
-        }
-    }
-    return i;
-}
-
-/* Returns the number of 1-bits in the 'n'-bit bitmap at 'bitmap'. */
-size_t
-bitmap_count1(const unsigned long int *bitmap, size_t n)
-{
-    size_t i;
-    size_t count = 0;
-
-    BUILD_ASSERT(ULONG_MAX <= UINT64_MAX);
-    for (i = 0; i < BITMAP_N_LONGS(n); i++) {
-        count += count_1bits(bitmap[i]);
-    }
-
-    return count;
-}
-
-/* "dst &= arg;" for n-bit dst and arg.  */
-void
-bitmap_and(unsigned long *dst, const unsigned long *arg, size_t n)
-{
-    size_t i;
-
-    for (i = 0; i < BITMAP_N_LONGS(n); i++) {
-        dst[i] &= arg[i];
-    }
-}
-
-/* "dst |= arg;" for n-bit dst and arg.  */
-void
-bitmap_or(unsigned long *dst, const unsigned long *arg, size_t n)
-{
-    size_t i;
-
-    for (i = 0; i < BITMAP_N_LONGS(n); i++) {
-        dst[i] |= arg[i];
-    }
-}
-
-/* "dst = ~dst;" for n-bit dst.  */
-void
-bitmap_not(unsigned long *dst, size_t n)
-{
-    size_t i;
-
-    for (i = 0; i < n / BITMAP_ULONG_BITS; i++) {
-        dst[i] = ~dst[i];
-    }
-    if (n % BITMAP_ULONG_BITS) {
-        dst[i] ^= (1u << (n % BITMAP_ULONG_BITS)) - 1;
-    }
-}
-
-/* Returns true if all of the 'n' bits in 'bitmap' are 0,
- * false if at least one bit is a 1.*/
-bool
-bitmap_is_all_zeros(const unsigned long *bitmap, size_t n)
-{
-    return bitmap_scan(bitmap, true, 0, n) == n;
-}

lib/bitmap.h

@@ -55,7 +55,27 @@ bitmap_allocate(size_t n_bits)
     return xzalloc(bitmap_n_bytes(n_bits));
 }
 
-unsigned long *bitmap_allocate1(size_t n_bits);
+/* Initializes bitmap to all-1-bits and returns the bitmap pointer. */
+static inline unsigned long *
+bitmap_init1(unsigned long *bitmap, size_t n_bits)
+{
+    size_t n_longs = bitmap_n_longs(n_bits);
+    size_t n_bytes = bitmap_n_bytes(n_bits);
+    size_t r_bits = n_bits % BITMAP_ULONG_BITS;
+
+    memset(bitmap, 0xff, n_bytes);
+    if (r_bits) {
+        bitmap[n_longs - 1] >>= BITMAP_ULONG_BITS - r_bits;
+    }
+    return bitmap;
+}
+
+/* Allocates and returns a bitmap initialized to all-1-bits. */
+static inline unsigned long *
+bitmap_allocate1(size_t n_bits)
+{
+    return bitmap_init1(xmalloc(bitmap_n_bytes(n_bits)), n_bits);
+}
 
 static inline unsigned long *
 bitmap_clone(const unsigned long *bitmap, size_t n_bits)
@@ -75,44 +95,179 @@ bitmap_is_set(const unsigned long *bitmap, size_t offset)
     return (*bitmap_unit__(bitmap, offset) & bitmap_bit__(offset)) != 0;
 }
 
-static inline void
+static inline unsigned long *
 bitmap_set1(unsigned long *bitmap, size_t offset)
 {
     *bitmap_unit__(bitmap, offset) |= bitmap_bit__(offset);
+    return bitmap;
 }
 
-static inline void
+static inline unsigned long *
 bitmap_set0(unsigned long *bitmap, size_t offset)
 {
     *bitmap_unit__(bitmap, offset) &= ~bitmap_bit__(offset);
+    return bitmap;
 }
 
-static inline void
+static inline unsigned long *
 bitmap_set(unsigned long *bitmap, size_t offset, bool value)
 {
+    return (value) ? bitmap_set1(bitmap, offset) : bitmap_set0(bitmap, offset);
+}
+
+/* Sets 'n' bits of a single unit. */
+static inline void
+bitmap_set_n__(unsigned long *bitmap, size_t start, size_t n, bool value)
+{
+    unsigned long mask = ((1UL << n) - 1) << start % BITMAP_ULONG_BITS;
+
     if (value) {
-        bitmap_set1(bitmap, offset);
+        *bitmap_unit__(bitmap, start) |= mask;
     } else {
-        bitmap_set0(bitmap, offset);
+        *bitmap_unit__(bitmap, start) &= ~mask;
     }
 }
 
-void bitmap_set_multiple(unsigned long *, size_t start, size_t count,
+/* Sets 'count' consecutive bits in 'bitmap', starting at bit offset 'start',
-                         bool value);
+ * to 'value'. */
-bool bitmap_equal(const unsigned long *, const unsigned long *, size_t n);
+static inline unsigned long *
-size_t bitmap_scan(const unsigned long int *, bool target,
+bitmap_set_multiple(unsigned long *bitmap, size_t start, size_t count,
-                   size_t start, size_t end);
+                    bool value)
-size_t bitmap_count1(const unsigned long *, size_t n);
+{
+    if (count && start % BITMAP_ULONG_BITS) {
+        size_t n = MIN(count, BITMAP_ULONG_BITS - start % BITMAP_ULONG_BITS);
 
-void bitmap_and(unsigned long *dst, const unsigned long *arg, size_t n);
+        bitmap_set_n__(bitmap, start, n, value);
-void bitmap_or(unsigned long *dst, const unsigned long *arg, size_t n);
+        count -= n;
-void bitmap_not(unsigned long *dst, size_t n);
+        start += n;
+    }
+    for (; count >= BITMAP_ULONG_BITS; count -= BITMAP_ULONG_BITS) {
+        *bitmap_unit__(bitmap, start) = (unsigned long)!value - 1;
+        start += BITMAP_ULONG_BITS;
+    }
+    if (count) {
+        bitmap_set_n__(bitmap, start, count, value);
+    }
+    return bitmap;
+}
 
-bool bitmap_is_all_zeros(const unsigned long *, size_t n);
+/* Returns the number of 1-bits in the 'n'-bit bitmap at 'bitmap'. */
+static inline size_t
+bitmap_count1(const unsigned long int *bitmap, size_t n)
+{
+    size_t i;
+    size_t count = 0;
 
-#define BITMAP_FOR_EACH_1(IDX, SIZE, BITMAP) \
+    BUILD_ASSERT(ULONG_MAX <= UINT64_MAX);
-    for ((IDX) = bitmap_scan(BITMAP, 1, 0, SIZE); (IDX) < (SIZE);    \
+    for (i = 0; i < BITMAP_N_LONGS(n); i++) {
-         (IDX) = bitmap_scan(BITMAP, 1, (IDX) + 1, SIZE))
+        count += count_1bits(bitmap[i]);
+    }
+    return count;
+}
+
+/* "dst &= arg;" for n-bit dst and arg.  */
+static inline unsigned long *
+bitmap_and(unsigned long *dst, const unsigned long *arg, size_t n)
+{
+    size_t i;
+
+    for (i = 0; i < BITMAP_N_LONGS(n); i++) {
+        dst[i] &= arg[i];
+    }
+    return dst;
+}
+
+/* "dst |= arg;" for n-bit dst and arg.  */
+static inline unsigned long *
+bitmap_or(unsigned long *dst, const unsigned long *arg, size_t n)
+{
+    size_t i;
+
+    for (i = 0; i < BITMAP_N_LONGS(n); i++) {
+        dst[i] |= arg[i];
+    }
+    return dst;
+}
+
+/* "dst = ~dst;" for n-bit dst.  */
+static inline unsigned long *
+bitmap_not(unsigned long *dst, size_t n)
+{
+    size_t i;
+
+    for (i = 0; i < n / BITMAP_ULONG_BITS; i++) {
+        dst[i] = ~dst[i];
+    }
+    if (n % BITMAP_ULONG_BITS) {
+        dst[i] ^= (1UL << (n % BITMAP_ULONG_BITS)) - 1;
+    }
+    return dst;
+}
+
+/* Compares the 'n' bits in bitmaps 'a' and 'b'.  Returns true if all bits are
+ * equal, false otherwise. */
+static inline bool
+bitmap_equal(const unsigned long *a, const unsigned long *b, size_t n)
+{
+    if (memcmp(a, b, n / BITMAP_ULONG_BITS * sizeof(unsigned long))) {
+        return false;
+    }
+    if (n % BITMAP_ULONG_BITS) {
+        unsigned long mask = (1UL << n % BITMAP_ULONG_BITS) - 1;
+        unsigned long diff = *bitmap_unit__(a, n) ^ *bitmap_unit__(b, n);
+
+        return !(diff & mask);
+    }
+    return true;
+}
+
+/* Scans 'bitmap' from bit offset 'start' to 'end', excluding 'end' itself.
+ * Returns the bit offset of the lowest-numbered bit set to 'target', or 'end'
+ * if all of the bits are set to '!target'.  'target' is typically a
+ * compile-time constant, so it makes sense to inline this.  Compiler may also
+ * optimize parts away depending on the 'start' and 'end' values passed in. */
+static inline size_t
+bitmap_scan(const unsigned long *bitmap, bool target, size_t start, size_t end)
+{
+    if (OVS_LIKELY(start < end)) {
+        unsigned long *p, unit;
+
+        p = bitmap_unit__(bitmap, start);
+        unit = (target ? *p : ~*p) >> (start % BITMAP_ULONG_BITS);
+        if (!unit) {
+            start -= start % BITMAP_ULONG_BITS; /* Round down. */
+            start += BITMAP_ULONG_BITS; /* Start of the next unit. */
+
+            for (; start < end; start += BITMAP_ULONG_BITS) {
+                unit = target ? *++p : ~*++p;
+                if (unit) {
+                    goto found;
+                }
+            }
+            return end;
+        }
+found:
+        start += raw_ctz(unit);  /* unit != 0 */
+        if (OVS_LIKELY(start < end)) {
+            return start;
+        }
+    }
+    return end;
+}
+
+/* Returns true if all of the 'n' bits in 'bitmap' are 0,
+ * false if at least one bit is a 1.*/
+static inline bool
+bitmap_is_all_zeros(const unsigned long *bitmap, size_t n)
+{
+    return bitmap_scan(bitmap, true, 0, n) == n;
+}
+
+#define BITMAP_FOR_EACH_1_RANGE(IDX, BEGIN, END, BITMAP)           \
+    for ((IDX) = bitmap_scan(BITMAP, true, BEGIN, END); (IDX) < (END);   \
+         (IDX) = bitmap_scan(BITMAP, true, (IDX) + 1, END))
+#define BITMAP_FOR_EACH_1(IDX, SIZE, BITMAP)        \
+    BITMAP_FOR_EACH_1_RANGE(IDX, 0, SIZE, BITMAP)
 
 /* More efficient access to a map of single ulong. */
 #define ULONG_FOR_EACH_1(IDX, MAP)                  \

lib/util.h

@@ -512,7 +512,7 @@ zero_rightmost_1bit(uintmax_t x)
  *
  * Unlike the other functions for rightmost 1-bits, this function only works
  * with 32-bit integers. */
-static inline uint32_t
+static inline int
 rightmost_1bit_idx(uint32_t x)
 {
     return ctz32(x);

tests/test-bitmap.c

@@ -82,12 +82,12 @@ test_bitmap_scan(void)
     bitmap_set1(a, MAX_BITS - 1);
     assert(bitmap_scan(a, true, 0, MAX_BITS) == MAX_BITS - 1);
     bitmap_set1(a, MAX_BITS - BITMAP_ULONG_BITS + 1);
-    assert(bitmap_scan(a, true, 0, MAX_BITS - 1)
+    assert(bitmap_scan(a, true, 3, MAX_BITS)
            == MAX_BITS - BITMAP_ULONG_BITS + 1);
     bitmap_set1(a, BITMAP_ULONG_BITS - 1);
-    assert(bitmap_scan(a, true, 0, MAX_BITS - 1) == BITMAP_ULONG_BITS - 1);
+    assert(bitmap_scan(a, true, 7, MAX_BITS - 1) == BITMAP_ULONG_BITS - 1);
     bitmap_set1(a, 0);
-    assert(bitmap_scan(a, true, 0, MAX_BITS - 1) == 0);
+    assert(bitmap_scan(a, true, 0, MAX_BITS - 7) == 0);
 
     bitmap_set_multiple(a, 0, MAX_BITS, true);
 
@@ -104,12 +104,12 @@ test_bitmap_scan(void)
     bitmap_set0(a, MAX_BITS - 1);
     assert(bitmap_scan(a, false, 0, MAX_BITS) == MAX_BITS - 1);
     bitmap_set0(a, MAX_BITS - BITMAP_ULONG_BITS + 1);
-    assert(bitmap_scan(a, false, 0, MAX_BITS - 1)
+    assert(bitmap_scan(a, false, 3, MAX_BITS)
            == MAX_BITS - BITMAP_ULONG_BITS + 1);
     bitmap_set0(a, BITMAP_ULONG_BITS - 1);
-    assert(bitmap_scan(a, false, 0, MAX_BITS - 1) == BITMAP_ULONG_BITS - 1);
+    assert(bitmap_scan(a, false, 7, MAX_BITS - 1) == BITMAP_ULONG_BITS - 1);
     bitmap_set0(a, 0);
-    assert(bitmap_scan(a, false, 0, MAX_BITS - 1) == 0);
+    assert(bitmap_scan(a, false, 0, MAX_BITS - 7) == 0);
 
     free(a);
 }