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Make dss operations lockless.

Browse source 
Rather than protecting dss operations with a mutex, use atomic
operations.  This has negligible impact on synchronization overhead
during typical dss allocation, but is a substantial improvement for
chunk_in_dss() and the newly added chunk_dss_mergeable(), which can be
called multiple times during chunk deallocations.

This change also has the advantage of avoiding tsd in deallocation paths
associated with purging, which resolves potential deadlocks during
thread exit due to attempted tsd resurrection.

This resolves #425.
This commit is contained in:
Jason Evans 2016-10-13 12:18:38 -07:00
parent 9737685943
commit e2bcf037d4
11 changed files with 134 additions and 153 deletions
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6
src/jemalloc.c
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@ -1115,8 +1115,7 @@ malloc_conf_init(void)
for (i = 0; i < dss_prec_limit; i++) {
if (strncmp(dss_prec_names[i], v, vlen)
== 0) {
if (chunk_dss_prec_set(NULL,
i)) {
if (chunk_dss_prec_set(i)) {
malloc_conf_error(
"Error setting dss",
k, klen, v, vlen);
@ -2783,7 +2782,6 @@ _malloc_prefork(void)
}
}
base_prefork(tsd_tsdn(tsd));
chunk_prefork(tsd_tsdn(tsd));
for (i = 0; i < narenas; i++) {
if ((arena = arena_get(tsd_tsdn(tsd), i, false)) != NULL)
arena_prefork3(tsd_tsdn(tsd), arena);
@ -2812,7 +2810,6 @@ _malloc_postfork(void)
witness_postfork_parent(tsd);
/* Release all mutexes, now that fork() has completed. */
chunk_postfork_parent(tsd_tsdn(tsd));
base_postfork_parent(tsd_tsdn(tsd));
for (i = 0, narenas = narenas_total_get(); i < narenas; i++) {
arena_t *arena;
@ -2837,7 +2834,6 @@ jemalloc_postfork_child(void)
witness_postfork_child(tsd);
/* Release all mutexes, now that fork() has completed. */
chunk_postfork_child(tsd_tsdn(tsd));
base_postfork_child(tsd_tsdn(tsd));
for (i = 0, narenas = narenas_total_get(); i < narenas; i++) {
arena_t *arena;