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Flat bitmap: Add longest-range computation.

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This will come in handy in the (upcoming) page-slab set assertions.
This commit is contained in:
David Goldblatt 2020-09-17 18:12:06 -07:00 committed by David Goldblatt
parent e034500698
commit ed99d300b9
2 changed files with 66 additions and 0 deletions
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25
include/jemalloc/internal/flat_bitmap.h
View File

@ -284,4 +284,29 @@ fb_urange_riter(fb_group_t *fb, size_t nbits, size_t start, size_t *r_begin,
/* val */ false, /* forward */ false);
}
JEMALLOC_ALWAYS_INLINE size_t
fb_range_longest_impl(fb_group_t *fb, size_t nbits, bool val) {
size_t begin = 0;
size_t longest_len = 0;
size_t len = 0;
while (begin < nbits && fb_iter_range_impl(fb, nbits, begin, &begin,
&len, val, /* forward */ true)) {
if (len > longest_len) {
longest_len = len;
}
begin += len;
}
return longest_len;
}
static inline size_t
fb_srange_longest(fb_group_t *fb, size_t nbits) {
return fb_range_longest_impl(fb, nbits, /* val */ true);
}
static inline size_t
fb_urange_longest(fb_group_t *fb, size_t nbits) {
return fb_range_longest_impl(fb, nbits, /* val */ false);
}
#endif /* JEMALLOC_INTERNAL_FB_H */

41
test/unit/flat_bitmap.c
View File

@ -301,6 +301,10 @@ TEST_BEGIN(test_empty_full) {
}
TEST_END
/*
* This tests both iter_range and the longest range functionality, which is
* built closely on top of it.
*/
TEST_BEGIN(test_iter_range_simple) {
size_t set_limit = 30;
size_t nbits = 100;
@ -318,6 +322,10 @@ TEST_BEGIN(test_iter_range_simple) {
/* A set of checks with only the first set_limit bits *set*. */
fb_set_range(fb, nbits, 0, set_limit);
expect_zu_eq(set_limit, fb_srange_longest(fb, nbits),
"Incorrect longest set range");
expect_zu_eq(nbits - set_limit, fb_urange_longest(fb, nbits),
"Incorrect longest unset range");
for (size_t i = 0; i < set_limit; i++) {
result = fb_srange_iter(fb, nbits, i, &begin, &len);
expect_true(result, "Should have found a range at %zu", i);
@ -360,6 +368,10 @@ TEST_BEGIN(test_iter_range_simple) {
/* A set of checks with only the first set_limit bits *unset*. */
fb_unset_range(fb, nbits, 0, set_limit);
fb_set_range(fb, nbits, set_limit, nbits - set_limit);
expect_zu_eq(nbits - set_limit, fb_srange_longest(fb, nbits),
"Incorrect longest set range");
expect_zu_eq(set_limit, fb_urange_longest(fb, nbits),
"Incorrect longest unset range");
for (size_t i = 0; i < set_limit; i++) {
result = fb_srange_iter(fb, nbits, i, &begin, &len);
expect_true(result, "Should have found a range at %zu", i);
@ -436,6 +448,27 @@ fb_iter_simple(fb_group_t *fb, size_t nbits, size_t start, size_t *r_begin,
return false;
}
/* Similar, but for finding longest ranges. */
static size_t
fb_range_longest_simple(fb_group_t *fb, size_t nbits, bool val) {
size_t longest_so_far = 0;
for (size_t begin = 0; begin < nbits; begin++) {
if (fb_get(fb, nbits, begin) != val) {
continue;
}
size_t end = begin + 1;
for (; end < nbits; end++) {
if (fb_get(fb, nbits, end) != val) {
break;
}
}
if (end - begin > longest_so_far) {
longest_so_far = end - begin;
}
}
return longest_so_far;
}
static void
expect_iter_results_at(fb_group_t *fb, size_t nbits, size_t pos,
bool val, bool forward) {
@ -487,6 +520,10 @@ expect_iter_results(fb_group_t *fb, size_t nbits) {
expect_iter_results_at(fb, nbits, i, true, false);
expect_iter_results_at(fb, nbits, i, true, true);
}
expect_zu_eq(fb_range_longest_simple(fb, nbits, true),
fb_srange_longest(fb, nbits), "Longest range mismatch");
expect_zu_eq(fb_range_longest_simple(fb, nbits, false),
fb_urange_longest(fb, nbits), "Longest range mismatch");
}
static void
@ -527,6 +564,10 @@ do_test_iter_range_exhaustive(size_t nbits) {
free(fb);
}
/*
* Like test_iter_range_simple, this tests both iteration and longest-range
* computation.
*/
TEST_BEGIN(test_iter_range_exhaustive) {
#define NB(nbits) \
do_test_iter_range_exhaustive(nbits);