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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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25
src/chunk.c
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@@ -21,7 +21,7 @@ static extent_tree_t chunks_ad_mmap;
static extent_tree_t chunks_szad_dss;
static extent_tree_t chunks_ad_dss;
rtree_t *chunks_rtree;
rtree_t chunks_rtree;
/* Various chunk-related settings. */
size_t chunksize;
@@ -200,7 +200,7 @@ chunk_register(void *chunk, size_t size, bool base)
assert(CHUNK_ADDR2BASE(chunk) == chunk);
if (config_ivsalloc && !base) {
if (rtree_set(chunks_rtree, (uintptr_t)chunk, 1))
if (rtree_set(&chunks_rtree, (uintptr_t)chunk, chunk))
return (true);
}
if (config_stats || config_prof) {
@@ -395,7 +395,7 @@ chunk_dalloc_core(void *chunk, size_t size)
assert((size & chunksize_mask) == 0);
if (config_ivsalloc)
rtree_set(chunks_rtree, (uintptr_t)chunk, 0);
rtree_set(&chunks_rtree, (uintptr_t)chunk, NULL);
if (config_stats || config_prof) {
malloc_mutex_lock(&chunks_mtx);
assert(stats_chunks.curchunks >= (size / chunksize));
@@ -415,6 +415,14 @@ chunk_dalloc_default(void *chunk, size_t size, unsigned arena_ind)
return (false);
}
static rtree_node_elm_t *
chunks_rtree_node_alloc(size_t nelms)
{
return ((rtree_node_elm_t *)base_alloc(nelms *
sizeof(rtree_node_elm_t)));
}
bool
chunk_boot(void)
{
@@ -436,9 +444,8 @@ chunk_boot(void)
extent_tree_szad_new(&chunks_szad_dss);
extent_tree_ad_new(&chunks_ad_dss);
if (config_ivsalloc) {
chunks_rtree = rtree_new((ZU(1) << (LG_SIZEOF_PTR+3)) -
opt_lg_chunk, base_alloc, NULL);
if (chunks_rtree == NULL)
if (rtree_new(&chunks_rtree, (ZU(1) << (LG_SIZEOF_PTR+3)) -
opt_lg_chunk, chunks_rtree_node_alloc, NULL))
return (true);
}
@@ -450,8 +457,6 @@ chunk_prefork(void)
{
malloc_mutex_prefork(&chunks_mtx);
if (config_ivsalloc)
rtree_prefork(chunks_rtree);
chunk_dss_prefork();
}
@@ -460,8 +465,6 @@ chunk_postfork_parent(void)
{
chunk_dss_postfork_parent();
if (config_ivsalloc)
rtree_postfork_parent(chunks_rtree);
malloc_mutex_postfork_parent(&chunks_mtx);
}
@@ -470,7 +473,5 @@ chunk_postfork_child(void)
{
chunk_dss_postfork_child();
if (config_ivsalloc)
rtree_postfork_child(chunks_rtree);
malloc_mutex_postfork_child(&chunks_mtx);
}