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Refactor rtree to be lock-free.

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Recent huge allocation refactoring associates huge allocations with
arenas, but it remains necessary to quickly look up huge allocation
metadata during reallocation/deallocation.  A global radix tree remains
a good solution to this problem, but locking would have become the
primary bottleneck after (upcoming) migration of chunk management from
global to per arena data structures.

This lock-free implementation uses double-checked reads to traverse the
tree, so that in the steady state, each read or write requires only a
single atomic operation.

This implementation also assures that no more than two tree levels
actually exist, through a combination of careful virtual memory
allocation which makes large sparse nodes cheap, and skipping the root
node on x64 (possible because the top 16 bits are all 0 in practice).
This commit is contained in:
Jason Evans
2015-01-30 22:54:08 -08:00
parent c810fcea1f
commit 8d0e04d42f
7 changed files with 384 additions and 229 deletions
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77
test/unit/rtree.c
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@@ -1,14 +1,30 @@
#include "test/jemalloc_test.h"
static rtree_node_elm_t *
node_alloc(size_t nelms)
{
return (calloc(nelms, sizeof(rtree_node_elm_t)));
}
static void
node_dalloc(rtree_node_elm_t *node)
{
free(node);
}
TEST_BEGIN(test_rtree_get_empty)
{
unsigned i;
for (i = 1; i <= (sizeof(uintptr_t) << 3); i++) {
rtree_t *rtree = rtree_new(i, malloc, free);
assert_u_eq(rtree_get(rtree, 0), 0,
rtree_t rtree;
assert_false(rtree_new(&rtree, i, node_alloc, node_dalloc),
"Unexpected rtree_new() failure");
assert_ptr_eq(rtree_get(&rtree, 0), NULL,
"rtree_get() should return NULL for empty tree");
rtree_delete(rtree);
rtree_delete(&rtree);
}
}
TEST_END
@@ -16,19 +32,22 @@ TEST_END
TEST_BEGIN(test_rtree_extrema)
{
unsigned i;
extent_node_t node_a, node_b;
for (i = 1; i <= (sizeof(uintptr_t) << 3); i++) {
rtree_t *rtree = rtree_new(i, malloc, free);
rtree_t rtree;
assert_false(rtree_new(&rtree, i, node_alloc, node_dalloc),
"Unexpected rtree_new() failure");
rtree_set(rtree, 0, 1);
assert_u_eq(rtree_get(rtree, 0), 1,
rtree_set(&rtree, 0, &node_a);
assert_ptr_eq(rtree_get(&rtree, 0), &node_a,
"rtree_get() should return previously set value");
rtree_set(rtree, ~((uintptr_t)0), 1);
assert_u_eq(rtree_get(rtree, ~((uintptr_t)0)), 1,
rtree_set(&rtree, ~((uintptr_t)0), &node_b);
assert_ptr_eq(rtree_get(&rtree, ~((uintptr_t)0)), &node_b,
"rtree_get() should return previously set value");
rtree_delete(rtree);
rtree_delete(&rtree);
}
}
TEST_END
@@ -40,26 +59,30 @@ TEST_BEGIN(test_rtree_bits)
for (i = 1; i < (sizeof(uintptr_t) << 3); i++) {
uintptr_t keys[] = {0, 1,
(((uintptr_t)1) << (sizeof(uintptr_t)*8-i)) - 1};
rtree_t *rtree = rtree_new(i, malloc, free);
extent_node_t node;
rtree_t rtree;
assert_false(rtree_new(&rtree, i, node_alloc, node_dalloc),
"Unexpected rtree_new() failure");
for (j = 0; j < sizeof(keys)/sizeof(uintptr_t); j++) {
rtree_set(rtree, keys[j], 1);
rtree_set(&rtree, keys[j], &node);
for (k = 0; k < sizeof(keys)/sizeof(uintptr_t); k++) {
assert_u_eq(rtree_get(rtree, keys[k]), 1,
assert_ptr_eq(rtree_get(&rtree, keys[k]), &node,
"rtree_get() should return previously set "
"value and ignore insignificant key bits; "
"i=%u, j=%u, k=%u, set key=%#"PRIxPTR", "
"get key=%#"PRIxPTR, i, j, k, keys[j],
keys[k]);
}
assert_u_eq(rtree_get(rtree,
(((uintptr_t)1) << (sizeof(uintptr_t)*8-i))), 0,
assert_ptr_eq(rtree_get(&rtree,
(((uintptr_t)1) << (sizeof(uintptr_t)*8-i))), NULL,
"Only leftmost rtree leaf should be set; "
"i=%u, j=%u", i, j);
rtree_set(rtree, keys[j], 0);
rtree_set(&rtree, keys[j], NULL);
}
rtree_delete(rtree);
rtree_delete(&rtree);
}
}
TEST_END
@@ -68,37 +91,41 @@ TEST_BEGIN(test_rtree_random)
{
unsigned i;
sfmt_t *sfmt;
#define NSET 100
#define NSET 16
#define SEED 42
sfmt = init_gen_rand(SEED);
for (i = 1; i <= (sizeof(uintptr_t) << 3); i++) {
rtree_t *rtree = rtree_new(i, malloc, free);
uintptr_t keys[NSET];
extent_node_t node;
unsigned j;
rtree_t rtree;
assert_false(rtree_new(&rtree, i, node_alloc, node_dalloc),
"Unexpected rtree_new() failure");
for (j = 0; j < NSET; j++) {
keys[j] = (uintptr_t)gen_rand64(sfmt);
rtree_set(rtree, keys[j], 1);
assert_u_eq(rtree_get(rtree, keys[j]), 1,
rtree_set(&rtree, keys[j], &node);
assert_ptr_eq(rtree_get(&rtree, keys[j]), &node,
"rtree_get() should return previously set value");
}
for (j = 0; j < NSET; j++) {
assert_u_eq(rtree_get(rtree, keys[j]), 1,
assert_ptr_eq(rtree_get(&rtree, keys[j]), &node,
"rtree_get() should return previously set value");
}
for (j = 0; j < NSET; j++) {
rtree_set(rtree, keys[j], 0);
assert_u_eq(rtree_get(rtree, keys[j]), 0,
rtree_set(&rtree, keys[j], NULL);
assert_ptr_eq(rtree_get(&rtree, keys[j]), NULL,
"rtree_get() should return previously set value");
}
for (j = 0; j < NSET; j++) {
assert_u_eq(rtree_get(rtree, keys[j]), 0,
assert_ptr_eq(rtree_get(&rtree, keys[j]), NULL,
"rtree_get() should return previously set value");
}
rtree_delete(rtree);
rtree_delete(&rtree);
}
fini_gen_rand(sfmt);
#undef NSET