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optimized epoch waiting

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This commit is contained in:
joaquintides
2023-12-02 20:52:20 +01:00
parent 49ff2a63ea
commit 5af735827f
1 changed files with 27 additions and 15 deletions
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42
include/boost/unordered/detail/foa/concurrent_table.hpp
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@ -971,22 +971,27 @@ private:
using exclusive_bilock_guard=
reentrancy_bichecked<scoped_bilock<multimutex_type>>;
#if defined(BOOST_UNORDERED_LATCH_FREE)
using epoch_type=std::atomic<std::size_t>;
using epoch_array=cache_aligned_array<epoch_type,128>; // TODO: adapt 128 to the machine
#endif
#if defined(BOOST_UNORDERED_LATCH_FREE)
struct group_shared_lock_guard
{
group_shared_lock_guard(std::atomic_int& cs_):cs{cs_}{cs.store(1);}
~group_shared_lock_guard(){cs.store(0);}
group_shared_lock_guard(epoch_type& e_):e{e_}{++e;}
~group_shared_lock_guard(){++e;}
std::atomic_int& cs;
epoch_type& e;
};
struct group_exclusive_lock_guard
{
group_exclusive_lock_guard(
std::atomic_int& cs_,group_access::exclusive_lock_guard&& lck_):
cs{cs_},lck{std::move(lck_)}{cs.store(1);}
~group_exclusive_lock_guard(){cs.store(0);}
epoch_type& e_,group_access::exclusive_lock_guard&& lck_):
e{e_},lck{std::move(lck_)}{++e;}
~group_exclusive_lock_guard(){++e;}
std::atomic_int& cs;
epoch_type& e;
group_access::exclusive_lock_guard lck;
};
#else
@ -1047,7 +1052,7 @@ private:
inline group_shared_lock_guard access(group_shared,std::size_t pos)const
{
#if defined(BOOST_UNORDERED_LATCH_FREE)
return {csections[thread_id()%csections.size()]};
return {epochs[thread_id()%epochs.size()]};
#else
return this->arrays.group_accesses()[pos].shared_access();
#endif
@ -1058,7 +1063,7 @@ private:
{
#if defined(BOOST_UNORDERED_LATCH_FREE)
return {
csections[thread_id()%csections.size()],
epochs[thread_id()%epochs.size()],
this->arrays.group_accesses()[pos].exclusive_access()
};
#else
@ -1505,7 +1510,7 @@ private:
/* slot wasn't empty */
goto startover;
}
wait_for_csections(); // WHY BEFORE THE FOLLOWING?
wait_for_epochs(); // WHY BEFORE THE FOLLOWING?
if(BOOST_UNLIKELY(insert_counter(pos0)++!=counter)){
/* other thread inserted from pos0, need to start over */
pg->reset(n);
@ -1815,13 +1820,16 @@ private:
mutable multimutex_type mutexes;
#if defined(BOOST_UNORDERED_LATCH_FREE)
mutable cache_aligned_array<
std::atomic_int,128> csections;
static epoch_array epochs;
void wait_for_csections()const
static void wait_for_epochs()
{
for(std::size_t i=0;i<csections.size();++i){
while(csections[i].load(std::memory_order_acquire)){}
for(std::size_t i=0;i<epochs.size();++i){
auto e=epochs[i].load(std::memory_order_acquire),
e1=e|1u;
while(e==e1){
e=epochs[i].load(std::memory_order_acquire);
}
}
}
#endif
@ -1830,6 +1838,10 @@ private:
template<typename T,typename H,typename P,typename A>
std::atomic<std::size_t> concurrent_table<T,H,P,A>::thread_counter={};
template<typename T,typename H,typename P,typename A>
typename concurrent_table<T,H,P,A>::epoch_array
concurrent_table<T,H,P,A>::epochs={};
#if defined(BOOST_MSVC)
#pragma warning(pop) /* C4714 */
#endif