* [PATCH 5/5][_Hahtable] Prealloc nodes on copy
@ 2022-06-20 16:58 François Dumont
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From: François Dumont @ 2022-06-20 16:58 UTC (permalink / raw)
To: libstdc++; +Cc: gcc-patches
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libstdc++: [_Hashtable] Prealloc nodes on _Hashtable copy
Prealloc nodes on copy to reduce memory fragmentation of nodes. Create a new
assignment method which copy hashtable instances respecting order of
nodes in the
bucket rather than order of node in the singly-linked list.
libstdc++-v3/ChangeLog:
* include/bits/hashtable_policy.h: Include stl_tempbuf.h.
(_Hashtable_alloc<>::_M_allocate_node_ptr): New.
(_PreAllocHashtableNodes<>): New.
* include/bits/hashtable.h
(_Hashtable<>::__prealloc_hashtable_nodes_gen_t): New.
(_Hashtable<>::_M_assign_stable):New.
(_Hashtable<>::operator=(const _Hashtable&)): Use latter.
(_Hashtable(const _Hashtable&)): Likewise.
(_Hashtable(const _Hashtable&, const allocator_type&)): Likewise.
(_Hashtable(_Hashtable&&, __node_alloc_type&&, false_type)): Likewise.
* testsuite/util/exception/safety.h (setup_base::compare): Compare
containers
rather than compare iterators.
* testsuite/23_containers/unordered_multiset/cons/copy.cc (main):
Likewise.
Tested under Linux x86_64.
François
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diff --git a/libstdc++-v3/include/bits/hashtable.h b/libstdc++-v3/include/bits/hashtable.h
index 011a707605f..b497f16d017 100644
--- a/libstdc++-v3/include/bits/hashtable.h
+++ b/libstdc++-v3/include/bits/hashtable.h
@@ -290,6 +290,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__detail::_ReuseOrAllocNode<__node_alloc_type>;
using __alloc_node_gen_cache_bbegin_t =
__detail::_AllocNode<__node_alloc_type, __detail::_CacheBBeginPolicy>;
+ using __prealloc_hashtable_nodes_gen_t =
+ __detail::_PreAllocHashtableNodes<__node_alloc_type>;
+
using __node_builder_t =
__detail::_NodeBuilder<_ExtractKey>;
using __no_cache_bbegin_policy_t =
@@ -483,6 +486,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
void
_M_assign(_Ht&&, const _NodeGenerator&);
+ template<typename _Ht, typename _NodeGenerator>
+ void
+ _M_assign_stable(_Ht&&, const _NodeGenerator&);
+
void
_M_move_assign(_Hashtable&&, true_type);
@@ -1364,10 +1371,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_M_bucket_count = __ht._M_bucket_count;
_M_element_count = __ht._M_element_count;
_M_rehash_policy = __ht._M_rehash_policy;
- __alloc_node_gen_cache_bbegin_t __node_gen(*this);
__try
{
- _M_assign(__ht, __node_gen);
+ __prealloc_hashtable_nodes_gen_t __node_gen(__ht, *this);
+ _M_assign_stable(__ht, __node_gen);
}
__catch(...)
{
@@ -1487,6 +1494,72 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
}
+ template<typename _Key, typename _Value, typename _Alloc,
+ typename _ExtractKey, typename _Equal,
+ typename _Hash, typename _RangeHash, typename _Unused,
+ typename _RehashPolicy, typename _Traits>
+ template<typename _Ht, typename _NodeGenerator>
+ void
+ _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
+ _Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
+ _M_assign_stable(_Ht&& __ht, const _NodeGenerator& __node_gen)
+ {
+ __buckets_ptr __buckets = nullptr;
+ if (!_M_buckets)
+ _M_buckets = __buckets = _M_allocate_buckets(_M_bucket_count);
+
+ __try
+ {
+ if (!__ht._M_before_begin._M_nxt)
+ return;
+
+ __node_ptr __prev_n = nullptr;
+ for (std::size_t __bkt = 0; __bkt != _M_bucket_count; ++__bkt)
+ {
+ if (__ht._M_buckets[__bkt] == nullptr)
+ continue;
+
+ __node_ptr __ht_n =
+ static_cast<__node_ptr>(__ht._M_buckets[__bkt]->_M_nxt);
+ __node_ptr __prev_ht_n = __ht_n;
+ __node_base_ptr __nxt_bkt_n = __bkt < _M_bucket_count - 1
+ ? __ht._M_buckets[__bkt + 1] : nullptr;
+ do
+ {
+ __node_ptr __this_n
+ = __node_gen(__prev_n, __bkt,
+ __fwd_value_for<_Ht>(__ht_n->_M_v()));
+ this->_M_copy_code(*__this_n, *__ht_n);
+ if (__prev_n)
+ {
+ if (!_M_buckets[__bkt])
+ _M_buckets[__bkt] = __prev_n;
+ __prev_n->_M_nxt = __this_n;
+ }
+ else
+ {
+ _M_buckets[__bkt] = &_M_before_begin;
+ _M_before_begin._M_nxt = __this_n;
+ }
+
+ __prev_n = __this_n;
+ __prev_ht_n = __ht_n;
+ __ht_n = __ht_n->_M_next();
+ }
+ while (__ht_n
+ && __ht._M_is_nxt_in_bucket(__bkt, __prev_ht_n,
+ __nxt_bkt_n));
+ }
+ }
+ __catch(...)
+ {
+ clear();
+ if (__buckets)
+ _M_deallocate_buckets();
+ __throw_exception_again;
+ }
+ }
+
template<typename _Key, typename _Value, typename _Alloc,
typename _ExtractKey, typename _Equal,
typename _Hash, typename _RangeHash, typename _Unused,
@@ -1575,8 +1648,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_M_element_count(__ht._M_element_count),
_M_rehash_policy(__ht._M_rehash_policy)
{
- __alloc_node_gen_cache_bbegin_t __node_gen(*this);
- _M_assign(__ht, __node_gen);
+ __prealloc_hashtable_nodes_gen_t __node_gen(__ht, *this);
+ _M_assign_stable(__ht, __node_gen);
}
template<typename _Key, typename _Value, typename _Alloc,
@@ -1629,8 +1702,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_M_element_count(__ht._M_element_count),
_M_rehash_policy(__ht._M_rehash_policy)
{
- __alloc_node_gen_cache_bbegin_t __node_gen(*this);
- _M_assign(__ht, __node_gen);
+ __prealloc_hashtable_nodes_gen_t __node_gen(__ht, *this);
+ _M_assign_stable(__ht, __node_gen);
}
template<typename _Key, typename _Value, typename _Alloc,
@@ -1669,11 +1742,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
else
{
- __alloc_node_gen_cache_bbegin_t __node_gen(*this);
+ __prealloc_hashtable_nodes_gen_t __node_gen(__ht, *this);
using _Fwd_Ht = __conditional_t<
__move_if_noexcept_cond<value_type>::value,
const _Hashtable&, _Hashtable&&>;
- _M_assign(std::forward<_Fwd_Ht>(__ht), __node_gen);
+ _M_assign_stable(std::forward<_Fwd_Ht>(__ht), __node_gen);
__ht.clear();
}
}
diff --git a/libstdc++-v3/include/bits/hashtable_policy.h b/libstdc++-v3/include/bits/hashtable_policy.h
index ff206a6ed20..becafcd3249 100644
--- a/libstdc++-v3/include/bits/hashtable_policy.h
+++ b/libstdc++-v3/include/bits/hashtable_policy.h
@@ -37,6 +37,7 @@
#include <bits/stl_pair.h> // for std::pair
#include <ext/aligned_buffer.h> // for __gnu_cxx::__aligned_buffer
#include <ext/alloc_traits.h> // for std::__alloc_rebind
+#include <bits/stl_tempbuf.h> // for std::get_temporary_buffer.
#include <ext/numeric_traits.h> // for __gnu_cxx::__int_traits
namespace std _GLIBCXX_VISIBILITY(default)
@@ -291,6 +292,113 @@ namespace __detail
__hashtable_alloc& _M_h;
};
+ template<typename _NodeAlloc>
+ struct _PreAllocHashtableNodes
+ {
+ private:
+ using __node_alloc_type = _NodeAlloc;
+ using __hashtable_alloc = _Hashtable_alloc<__node_alloc_type>;
+ using __node_alloc_traits =
+ typename __hashtable_alloc::__node_alloc_traits;
+ using __node_base = typename __hashtable_alloc::__node_base;
+
+ public:
+ using __node_ptr = typename __hashtable_alloc::__node_ptr;
+
+ template<typename _Ht>
+ _PreAllocHashtableNodes(_Ht& __ht, __hashtable_alloc& __ha)
+ : _M_h(__ha), _M_before_free_nodes()
+ , _M_buckets(std::get_temporary_buffer<__node_base*>(__ht.bucket_count()))
+ {
+ __builtin_memset(_M_buckets.first, 0,
+ _M_buckets.second * sizeof(__node_base*));
+ __try
+ {
+ __node_ptr __hint = nullptr;
+ __node_base* __prev = std::__addressof(_M_before_free_nodes);
+ for (std::size_t __bkt = 0; __bkt != _M_buckets.second; ++__bkt)
+ for (auto __lit = __ht.begin(__bkt); __lit != __ht.end(__bkt);
+ ++__lit)
+ {
+ __node_ptr __tmp = _M_h._M_allocate_node_ptr(__hint);
+ if (!_M_buckets.first[__bkt])
+ _M_buckets.first[__bkt] = __prev;
+
+ __prev->_M_nxt = __tmp;
+ __prev = __hint = __tmp;
+ }
+ }
+ __catch(...)
+ {
+ _M_deallocate_nodes();
+ __throw_exception_again;
+ }
+ }
+
+ _PreAllocHashtableNodes(const _PreAllocHashtableNodes&) = delete;
+
+ ~_PreAllocHashtableNodes()
+ { _M_deallocate_nodes(); }
+
+ template<typename... _Args>
+ __node_ptr
+ operator()(__node_ptr __hint, std::size_t __bkt, _Args&&... __args) const
+ {
+ if (__bkt >= _M_buckets.second || _M_buckets.first[__bkt] == nullptr)
+ return _M_h._M_allocate_node(__hint,
+ std::forward<_Args>(__args)...);
+
+ if (_M_buckets.first[__bkt] != std::__addressof(_M_before_free_nodes))
+ {
+ _M_buckets.first[_M_last_access_bkt] = nullptr;
+ _M_buckets.first[__bkt] = std::__addressof(_M_before_free_nodes);
+ }
+
+ _M_last_access_bkt = __bkt;
+ auto __prev = _M_buckets.first[__bkt];
+ __node_ptr __node = static_cast<__node_ptr>(__prev->_M_nxt);
+ _M_before_free_nodes._M_nxt = __node->_M_nxt;
+ if (_M_before_free_nodes._M_nxt == nullptr)
+ _M_buckets.first[__bkt] = nullptr;
+
+ __node->_M_nxt = nullptr;
+ auto& __a = _M_h._M_node_allocator();
+ __try
+ {
+ __node_alloc_traits::construct(__a, __node->_M_valptr(),
+ std::forward<_Args>(__args)...);
+ }
+ __catch(...)
+ {
+ _M_h._M_deallocate_node_ptr(__node);
+ __throw_exception_again;
+ }
+
+ return __node;
+ }
+
+ private:
+ void
+ _M_deallocate_nodes()
+ {
+ __node_ptr __n
+ = static_cast<__node_ptr>(_M_before_free_nodes._M_nxt);
+ while (__n)
+ {
+ __node_ptr __tmp = __n;
+ __n = __n->_M_next();
+ _M_h._M_deallocate_node_ptr(__tmp);
+ }
+
+ std::return_temporary_buffer(_M_buckets.first);
+ }
+
+ mutable __node_base _M_before_free_nodes;
+ mutable std::pair<__node_base**, std::ptrdiff_t> _M_buckets;
+ mutable std::size_t _M_last_access_bkt = 0;
+ __hashtable_alloc& _M_h;
+ };
+
// Auxiliary types used for all instantiations of _Hashtable nodes
// and iterators.
@@ -2031,6 +2139,10 @@ namespace __detail
_M_node_allocator() const
{ return __ebo_node_alloc::_M_cget(); }
+ // Allocate a node.
+ __node_ptr
+ _M_allocate_node_ptr(__node_ptr __hint);
+
// Allocate a node and construct an element within it.
template<typename... _Args>
__node_ptr
@@ -2058,6 +2170,27 @@ namespace __detail
// Definitions of class template _Hashtable_alloc's out-of-line member
// functions.
+ template<typename _NodeAlloc>
+ auto
+ _Hashtable_alloc<_NodeAlloc>::_M_allocate_node_ptr(__node_ptr __hint)
+ -> __node_ptr
+ {
+ auto& __alloc = _M_node_allocator();
+ typename __node_alloc_traits::pointer __nptr;
+ if (__hint)
+ {
+ typedef typename __node_alloc_traits::const_pointer _CPtr;
+ auto __hptr = std::pointer_traits<_CPtr>::pointer_to(*__hint);
+ __nptr = __node_alloc_traits::allocate(__alloc, 1, __hptr);
+ }
+ else
+ __nptr = __node_alloc_traits::allocate(__alloc, 1);
+
+ __node_ptr __n = std::__to_address(__nptr);
+ ::new ((void*)__n) __node_type;
+ return __n;
+ }
+
template<typename _NodeAlloc>
template<typename... _Args>
auto
diff --git a/libstdc++-v3/testsuite/23_containers/unordered_multiset/cons/copy.cc b/libstdc++-v3/testsuite/23_containers/unordered_multiset/cons/copy.cc
index 22bedb9065f..c4e521ab662 100644
--- a/libstdc++-v3/testsuite/23_containers/unordered_multiset/cons/copy.cc
+++ b/libstdc++-v3/testsuite/23_containers/unordered_multiset/cons/copy.cc
@@ -38,6 +38,6 @@ int main()
std::unordered_multiset<int> copy(ref);
VERIFY( copy.size() == ref.size() );
- VERIFY( std::equal(ref.begin(), ref.end(), copy.begin()) );
+ VERIFY( copy == ref );
return 0;
}
diff --git a/libstdc++-v3/testsuite/util/exception/safety.h b/libstdc++-v3/testsuite/util/exception/safety.h
index 8ef91648af6..ad55812be1a 100644
--- a/libstdc++-v3/testsuite/util/exception/safety.h
+++ b/libstdc++-v3/testsuite/util/exception/safety.h
@@ -235,12 +235,11 @@ namespace __gnu_test
"setup_base::compare containers size not equal");
// Should test iterator validity before and after exception.
- bool __equal_it = std::equal(__test.begin(), __test.end(),
- __control.begin());
+ bool __equal = __test == __control;
- if (!__equal_it)
+ if (!__equal)
throw std::logic_error(
- "setup_base::compare containers iterators not equal");
+ "setup_base::compare containers not equal");
return true;
}
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