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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
extent_in_dss() and the newly added extent_dss_mergeable(), which can be
called multiple times during extent 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 e5effef428
commit 577d4572b0
11 changed files with 139 additions and 155 deletions
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48
src/extent.c
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@@ -856,10 +856,10 @@ extent_dalloc_cache(tsdn_t *tsdn, arena_t *arena,
}
static bool
extent_dalloc_default_impl(tsdn_t *tsdn, void *addr, size_t size)
extent_dalloc_default_impl(void *addr, size_t size)
{
if (!have_dss || !extent_in_dss(tsdn, addr))
if (!have_dss || !extent_in_dss(addr))
return (extent_dalloc_mmap(addr, size));
return (true);
}
@@ -869,13 +869,10 @@ static bool
extent_dalloc_default(extent_hooks_t *extent_hooks, void *addr, size_t size,
bool committed, unsigned arena_ind)
{
tsdn_t *tsdn;
assert(extent_hooks == &extent_hooks_default);
tsdn = tsdn_fetch();
return (extent_dalloc_default_impl(tsdn, addr, size));
return (extent_dalloc_default_impl(addr, size));
}
void
@@ -897,7 +894,7 @@ extent_dalloc_wrapper(tsdn_t *tsdn, arena_t *arena,
extent_deregister(tsdn, extent);
if (*r_extent_hooks == &extent_hooks_default) {
/* Call directly to propagate tsdn. */
err = extent_dalloc_default_impl(tsdn, extent_base_get(extent),
err = extent_dalloc_default_impl(extent_base_get(extent),
extent_size_get(extent));
} else {
err = (*r_extent_hooks)->dalloc(*r_extent_hooks,
@@ -1083,13 +1080,12 @@ label_error_a:
}
static bool
extent_merge_default_impl(tsdn_t *tsdn, void *addr_a, void *addr_b)
extent_merge_default_impl(void *addr_a, void *addr_b)
{
if (!maps_coalesce)
return (true);
if (have_dss && extent_in_dss(tsdn, addr_a) != extent_in_dss(tsdn,
addr_b))
if (have_dss && !extent_dss_mergeable(addr_a, addr_b))
return (true);
return (false);
@@ -1099,13 +1095,10 @@ static bool
extent_merge_default(extent_hooks_t *extent_hooks, void *addr_a, size_t size_a,
void *addr_b, size_t size_b, bool committed, unsigned arena_ind)
{
tsdn_t *tsdn;
assert(extent_hooks == &extent_hooks_default);
tsdn = tsdn_fetch();
return (extent_merge_default_impl(tsdn, addr_a, addr_b));
return (extent_merge_default_impl(addr_a, addr_b));
}
bool
@@ -1120,7 +1113,7 @@ extent_merge_wrapper(tsdn_t *tsdn, arena_t *arena,
extent_hooks_assure_initialized(arena, r_extent_hooks);
if (*r_extent_hooks == &extent_hooks_default) {
/* Call directly to propagate tsdn. */
err = extent_merge_default_impl(tsdn, extent_base_get(a),
err = extent_merge_default_impl(extent_base_get(a),
extent_base_get(b));
} else {
err = (*r_extent_hooks)->merge(*r_extent_hooks,
@@ -1171,29 +1164,8 @@ extent_boot(void)
LG_PAGE)))
return (true);
if (have_dss && extent_dss_boot())
return (true);
if (have_dss)
extent_dss_boot();
return (false);
}
void
extent_prefork(tsdn_t *tsdn)
{
extent_dss_prefork(tsdn);
}
void
extent_postfork_parent(tsdn_t *tsdn)
{
extent_dss_postfork_parent(tsdn);
}
void
extent_postfork_child(tsdn_t *tsdn)
{
extent_dss_postfork_child(tsdn);
}