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Made the mem_cache_block lockfree

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This *significantly* improves parallel performance of regex.
Currently if I have a large number of threads all using regexes; even if
they are using idependent regex objects, performance is still extremely poor
due to the lock inside of the mem_block_cache.
This commit is contained in:
Yucheng Low
2015-12-08 21:17:50 -08:00
parent eb729f6557
commit b9f55efe98
2 changed files with 28 additions and 48 deletions
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72
include/boost/regex/v4/mem_block_cache.hpp
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@ -19,9 +19,7 @@
#define BOOST_REGEX_V4_MEM_BLOCK_CACHE_HPP
#include <new>
#ifdef BOOST_HAS_THREADS
#include <boost/regex/pending/static_mutex.hpp>
#endif
#include <boost/atomic/atomic.hpp>
#ifdef BOOST_HAS_ABI_HEADERS
# include BOOST_ABI_PREFIX
@ -30,59 +28,41 @@
namespace boost{
namespace BOOST_REGEX_DETAIL_NS{
struct mem_block_node
{
mem_block_node* next;
};
struct mem_block_cache
{
// this member has to be statically initialsed:
mem_block_node* next;
unsigned cached_blocks;
#ifdef BOOST_HAS_THREADS
boost::static_mutex mut;
#endif
boost::atomic<void*> cache[BOOST_REGEX_MAX_CACHE_BLOCKS];
mem_block_cache() {
for (size_t i = 0;i < BOOST_REGEX_MAX_CACHE_BLOCKS; ++i) {
cache[i].store(NULL);
}
}
~mem_block_cache()
{
while(next)
{
mem_block_node* old = next;
next = next->next;
::operator delete(old);
}
for (size_t i = 0;i < BOOST_REGEX_MAX_CACHE_BLOCKS; ++i) {
if (cache[i].load()) ::operator delete(cache[i].load());
}
}
void* get()
{
#ifdef BOOST_HAS_THREADS
boost::static_mutex::scoped_lock g(mut);
#endif
if(next)
{
mem_block_node* result = next;
next = next->next;
--cached_blocks;
return result;
}
return ::operator new(BOOST_REGEX_BLOCKSIZE);
for (size_t i = 0;i < BOOST_REGEX_MAX_CACHE_BLOCKS; ++i) {
void* p = cache[i].load();
if (p != NULL) {
if (cache[i].compare_exchange_strong(p, NULL)) return p;
}
}
return ::operator new(BOOST_REGEX_BLOCKSIZE);
}
void put(void* p)
void put(void* ptr)
{
#ifdef BOOST_HAS_THREADS
boost::static_mutex::scoped_lock g(mut);
#endif
if(cached_blocks >= BOOST_REGEX_MAX_CACHE_BLOCKS)
{
::operator delete(p);
}
else
{
mem_block_node* old = static_cast<mem_block_node*>(p);
old->next = next;
next = old;
++cached_blocks;
}
for (size_t i = 0;i < BOOST_REGEX_MAX_CACHE_BLOCKS; ++i) {
void* p = cache[i].load();
if (p == NULL) {
if (cache[i].compare_exchange_strong(p, ptr)) return;
}
}
::operator delete(ptr);
}
};