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Implement bitmap_ffu(), which finds the first unset bit.

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This commit is contained in:
Jason Evans 2017-03-23 17:59:47 -07:00
parent a832ebaee9
commit c8021d01f6
6 changed files with 136 additions and 25 deletions
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2
include/jemalloc/internal/bitmap_externs.h
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@ -2,7 +2,7 @@
#define JEMALLOC_INTERNAL_BITMAP_EXTERNS_H
void bitmap_info_init(bitmap_info_t *binfo, size_t nbits);
void bitmap_init(bitmap_t *bitmap, const bitmap_info_t *binfo);
void bitmap_init(bitmap_t *bitmap, const bitmap_info_t *binfo, bool fill);
size_t bitmap_size(const bitmap_info_t *binfo);
#endif /* JEMALLOC_INTERNAL_BITMAP_EXTERNS_H */

60
include/jemalloc/internal/bitmap_inlines.h
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@ -5,6 +5,8 @@
bool bitmap_full(bitmap_t *bitmap, const bitmap_info_t *binfo);
bool bitmap_get(bitmap_t *bitmap, const bitmap_info_t *binfo, size_t bit);
void bitmap_set(bitmap_t *bitmap, const bitmap_info_t *binfo, size_t bit);
size_t bitmap_ffu(const bitmap_t *bitmap, const bitmap_info_t *binfo,
size_t min_bit);
size_t bitmap_sfu(bitmap_t *bitmap, const bitmap_info_t *binfo);
void bitmap_unset(bitmap_t *bitmap, const bitmap_info_t *binfo, size_t bit);
#endif
@ -75,6 +77,64 @@ bitmap_set(bitmap_t *bitmap, const bitmap_info_t *binfo, size_t bit) {
#endif
}
/* ffu: find first unset >= bit. */
JEMALLOC_INLINE size_t
bitmap_ffu(const bitmap_t *bitmap, const bitmap_info_t *binfo, size_t min_bit) {
assert(min_bit < binfo->nbits);
#ifdef BITMAP_USE_TREE
unsigned level = binfo->nlevels - 1;
size_t lg_bits_per_group = (LG_BITMAP_GROUP_NBITS * (level+1));
size_t bits_per_group = 1LU << lg_bits_per_group;
size_t bits_per_group_mask = bits_per_group - 1;
unsigned group_nmask = (min_bit & bits_per_group_mask) >> (level *
LG_BITMAP_GROUP_NBITS);
bitmap_t group_mask = ~((1LU << group_nmask) - 1);
bitmap_t group = bitmap[binfo->levels[level].group_offset] & group_mask;
if (group == 0LU) {
return binfo->nbits;
}
size_t bit = ffs_lu(group) - 1;
while (level > 0) {
level--;
lg_bits_per_group = (LG_BITMAP_GROUP_NBITS * (level+1));
bits_per_group = 1LU << lg_bits_per_group;
bits_per_group_mask = bits_per_group - 1;
group = bitmap[binfo->levels[level].group_offset + bit];
size_t cur_base = bit << lg_bits_per_group;
if (cur_base < min_bit) {
group_nmask = (min_bit & bits_per_group_mask) >> (level
* LG_BITMAP_GROUP_NBITS);
group_mask = ~((1LU << group_nmask) - 1);
group &= group_mask;
}
if (group == 0LU) {
return binfo->nbits;
}
bit = (bit << LG_BITMAP_GROUP_NBITS) + (ffs_lu(group) - 1);
}
assert(bit < binfo->nbits);
return bit;
#else
size_t i = min_bit >> LG_BITMAP_GROUP_NBITS;
bitmap_t g = bitmap[i] & ~((1LU << (min_bit & BITMAP_GROUP_NBITS_MASK))
- 1);
size_t bit;
do {
bit = ffs_lu(g);
if (bit != 0) {
return (i << LG_BITMAP_GROUP_NBITS) + (bit - 1);
}
i++;
g = bitmap[i];
} while (i < binfo->ngroups);
return binfo->nbits;
#endif
}
/* sfu: set first unset. */
JEMALLOC_INLINE size_t
bitmap_sfu(bitmap_t *bitmap, const bitmap_info_t *binfo) {

1
include/jemalloc/internal/private_symbols.txt
View File

@ -94,6 +94,7 @@ base_postfork_child
base_postfork_parent
base_prefork
base_stats_get
bitmap_ffu
bitmap_full
bitmap_get
bitmap_info_init

2
src/arena.c
View File

@ -1210,7 +1210,7 @@ arena_slab_alloc(tsdn_t *tsdn, arena_t *arena, szind_t binind,
/* Initialize slab internals. */
arena_slab_data_t *slab_data = extent_slab_data_get(slab);
slab_data->nfree = bin_info->nregs;
bitmap_init(slab_data->bitmap, &bin_info->bitmap_info);
bitmap_init(slab_data->bitmap, &bin_info->bitmap_info, false);
arena_nactive_add(arena, extent_size_get(slab) >> LG_PAGE);

27
src/bitmap.c
View File

@ -39,16 +39,26 @@ bitmap_info_ngroups(const bitmap_info_t *binfo) {
}
void
bitmap_init(bitmap_t *bitmap, const bitmap_info_t *binfo) {
bitmap_init(bitmap_t *bitmap, const bitmap_info_t *binfo, bool fill) {
size_t extra;
unsigned i;
/*
* Bits are actually inverted with regard to the external bitmap
* interface, so the bitmap starts out with all 1 bits, except for
* trailing unused bits (if any). Note that each group uses bit 0 to
* correspond to the first logical bit in the group, so extra bits
* are the most significant bits of the last group.
* interface.
*/
if (fill) {
/* The "filled" bitmap starts out with all 0 bits. */
memset(bitmap, 0, bitmap_size(binfo));
return;
}
/*
* The "empty" bitmap starts out with all 1 bits, except for trailing
* unused bits (if any). Note that each group uses bit 0 to correspond
* to the first logical bit in the group, so extra bits are the most
* significant bits of the last group.
*/
memset(bitmap, 0xffU, bitmap_size(binfo));
extra = (BITMAP_GROUP_NBITS - (binfo->nbits & BITMAP_GROUP_NBITS_MASK))
@ -84,9 +94,14 @@ bitmap_info_ngroups(const bitmap_info_t *binfo) {
}
void
bitmap_init(bitmap_t *bitmap, const bitmap_info_t *binfo) {
bitmap_init(bitmap_t *bitmap, const bitmap_info_t *binfo, bool fill) {
size_t extra;
if (fill) {
memset(bitmap, 0, bitmap_size(binfo));
return;
}
memset(bitmap, 0xffU, bitmap_size(binfo));
extra = (BITMAP_GROUP_NBITS - (binfo->nbits & BITMAP_GROUP_NBITS_MASK))
& BITMAP_GROUP_NBITS_MASK;

59
test/unit/bitmap.c
View File

@ -171,12 +171,18 @@ test_bitmap_init_body(const bitmap_info_t *binfo, size_t nbits) {
size_t i;
bitmap_t *bitmap = (bitmap_t *)malloc(bitmap_size(binfo));
assert_ptr_not_null(bitmap, "Unexpected malloc() failure");
bitmap_init(bitmap, binfo);
bitmap_init(bitmap, binfo, false);
for (i = 0; i < nbits; i++) {
assert_false(bitmap_get(bitmap, binfo, i),
"Bit should be unset");
}
bitmap_init(bitmap, binfo, true);
for (i = 0; i < nbits; i++) {
assert_true(bitmap_get(bitmap, binfo, i), "Bit should be set");
}
free(bitmap);
}
@ -202,7 +208,7 @@ test_bitmap_set_body(const bitmap_info_t *binfo, size_t nbits) {
size_t i;
bitmap_t *bitmap = (bitmap_t *)malloc(bitmap_size(binfo));
assert_ptr_not_null(bitmap, "Unexpected malloc() failure");
bitmap_init(bitmap, binfo);
bitmap_init(bitmap, binfo, false);
for (i = 0; i < nbits; i++) {
bitmap_set(bitmap, binfo, i);
@ -233,7 +239,7 @@ test_bitmap_unset_body(const bitmap_info_t *binfo, size_t nbits) {
size_t i;
bitmap_t *bitmap = (bitmap_t *)malloc(bitmap_size(binfo));
assert_ptr_not_null(bitmap, "Unexpected malloc() failure");
bitmap_init(bitmap, binfo);
bitmap_init(bitmap, binfo, false);
for (i = 0; i < nbits; i++) {
bitmap_set(bitmap, binfo, i);
@ -268,14 +274,22 @@ TEST_END
static void
test_bitmap_sfu_body(const bitmap_info_t *binfo, size_t nbits) {
size_t i;
bitmap_t *bitmap = (bitmap_t *)malloc(bitmap_size(binfo));
assert_ptr_not_null(bitmap, "Unexpected malloc() failure");
bitmap_init(bitmap, binfo);
bitmap_init(bitmap, binfo, false);
/* Iteratively set bits starting at the beginning. */
for (i = 0; i < nbits; i++) {
assert_zd_eq(bitmap_sfu(bitmap, binfo), i,
for (size_t i = 0; i < nbits; i++) {
assert_zu_eq(bitmap_ffu(bitmap, binfo, 0), i,
"First unset bit should be just after previous first unset "
"bit");
assert_zu_eq(bitmap_ffu(bitmap, binfo, (i > 0) ? i-1 : i), i,
"First unset bit should be just after previous first unset "
"bit");
assert_zu_eq(bitmap_ffu(bitmap, binfo, i), i,
"First unset bit should be just after previous first unset "
"bit");
assert_zu_eq(bitmap_sfu(bitmap, binfo), i,
"First unset bit should be just after previous first unset "
"bit");
}
@ -285,9 +299,15 @@ test_bitmap_sfu_body(const bitmap_info_t *binfo, size_t nbits) {
* Iteratively unset bits starting at the end, and verify that
* bitmap_sfu() reaches the unset bits.
*/
for (i = nbits - 1; i < nbits; i--) { /* (nbits..0] */
for (size_t i = nbits - 1; i < nbits; i--) { /* (nbits..0] */
bitmap_unset(bitmap, binfo, i);
assert_zd_eq(bitmap_sfu(bitmap, binfo), i,
assert_zu_eq(bitmap_ffu(bitmap, binfo, 0), i,
"First unset bit should the bit previously unset");
assert_zu_eq(bitmap_ffu(bitmap, binfo, (i > 0) ? i-1 : i), i,
"First unset bit should the bit previously unset");
assert_zu_eq(bitmap_ffu(bitmap, binfo, i), i,
"First unset bit should the bit previously unset");
assert_zu_eq(bitmap_sfu(bitmap, binfo), i,
"First unset bit should the bit previously unset");
bitmap_unset(bitmap, binfo, i);
}
@ -297,14 +317,29 @@ test_bitmap_sfu_body(const bitmap_info_t *binfo, size_t nbits) {
* Iteratively set bits starting at the beginning, and verify that
* bitmap_sfu() looks past them.
*/
for (i = 1; i < nbits; i++) {
for (size_t i = 1; i < nbits; i++) {
bitmap_set(bitmap, binfo, i - 1);
assert_zd_eq(bitmap_sfu(bitmap, binfo), i,
assert_zu_eq(bitmap_ffu(bitmap, binfo, 0), i,
"First unset bit should be just after the bit previously "
"set");
assert_zu_eq(bitmap_ffu(bitmap, binfo, (i > 0) ? i-1 : i), i,
"First unset bit should be just after the bit previously "
"set");
assert_zu_eq(bitmap_ffu(bitmap, binfo, i), i,
"First unset bit should be just after the bit previously "
"set");
assert_zu_eq(bitmap_sfu(bitmap, binfo), i,
"First unset bit should be just after the bit previously "
"set");
bitmap_unset(bitmap, binfo, i);
}
assert_zd_eq(bitmap_sfu(bitmap, binfo), nbits - 1,
assert_zu_eq(bitmap_ffu(bitmap, binfo, 0), nbits - 1,
"First unset bit should be the last bit");
assert_zu_eq(bitmap_ffu(bitmap, binfo, (nbits > 1) ? nbits-2 : nbits-1),
nbits - 1, "First unset bit should be the last bit");
assert_zu_eq(bitmap_ffu(bitmap, binfo, nbits - 1), nbits - 1,
"First unset bit should be the last bit");
assert_zu_eq(bitmap_sfu(bitmap, binfo), nbits - 1,
"First unset bit should be the last bit");
assert_true(bitmap_full(bitmap, binfo), "All bits should be set");
free(bitmap);