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Index: include/ext/mt_allocator.h =================================================================== --- include/ext/mt_allocator.h (revision 116606) +++ include/ext/mt_allocator.h (working copy) @@ -298,8 +298,14 @@ // An "array" of counters used to keep track of the amount of // blocks that are on the freelist/used for each thread id. - // Memory to these "arrays" is allocated in _S_initialize() for - // _S_max_threads + global pool 0. + // - Note that the second half of the allocated _M_used "array" + // actually hosts (atomic) counters of reclaimed blocks: at + // deallocation time (in _M_reclaim_block) those numbers are + // subtracted from the first ones to obtain the actual size + // of the "working set" of the given thread, used by the + // removal heuristics. + // - Memory to these "arrays" is allocated in _S_initialize() + // for _S_max_threads + global pool 0. size_t* _M_free; size_t* _M_used; Index: src/mt_allocator.cc =================================================================== --- src/mt_allocator.cc (revision 116604) +++ src/mt_allocator.cc (working copy) @@ -34,6 +34,7 @@ #include <bits/c++config.h> #include <bits/concurrence.h> #include <ext/mt_allocator.h> +#include <cstring> namespace { @@ -263,17 +264,35 @@ // number of records is "high enough". const size_t __thread_id = _M_get_thread_id(); const _Tune& __options = _M_get_options(); - const unsigned long __limit = 100 * (_M_bin_size - __which) - * __options._M_freelist_headroom; + const size_t __limit = (100 * (_M_bin_size - __which) + * __options._M_freelist_headroom); - unsigned long __remove = __bin._M_free[__thread_id]; + size_t __remove = __bin._M_free[__thread_id]; __remove *= __options._M_freelist_headroom; - if (__remove >= __bin._M_used[__thread_id]) - __remove -= __bin._M_used[__thread_id]; + + // NB: We assume that reads of _Atomic_words are atomic. + const size_t __max_threads = __options._M_max_threads + 1; + _Atomic_word* const __reclaimed_base = + reinterpret_cast<_Atomic_word*>(__bin._M_used + __max_threads); + const _Atomic_word __reclaimed = __reclaimed_base[__thread_id]; + + // NB: We delay the actual update of _M_used[__thread_id] to + // the body of the conditional below, to spare an atomic. + // Note that when we actually enter it, __reclaimed is <= of + // the actual current __reclaimed_base[__thread_id], thus safe, + // because, between the read above and the atomic, the other + // threads can only have increased the latter (in the else 30 + // lines below). + const size_t __used = __bin._M_used[__thread_id] - __reclaimed; + if (__remove >= __used) + __remove -= __used; else __remove = 0; if (__remove > __limit && __remove > __bin._M_free[__thread_id]) { + __bin._M_used[__thread_id] -= __reclaimed; + __atomic_add(&__reclaimed_base[__thread_id], -__reclaimed); + _Block_record* __first = __bin._M_first[__thread_id]; _Block_record* __tmp = __first; __remove /= __options._M_freelist_headroom; @@ -292,8 +311,11 @@ // Return this block to our list and update counters and // owner id as needed. - --__bin._M_used[__block->_M_thread_id]; - + if (__block->_M_thread_id == __thread_id) + --__bin._M_used[__thread_id]; + else + __atomic_add(&__reclaimed_base[__block->_M_thread_id], 1); + __block->_M_next = __bin._M_first[__thread_id]; __bin._M_first[__thread_id] = __block; @@ -533,14 +555,19 @@ { _Bin_record& __bin = _M_bin[__n]; __v = ::operator new(sizeof(_Block_record*) * __max_threads); + std::memset(__v, 0, sizeof(_Block_record*) * __max_threads); __bin._M_first = static_cast<_Block_record**>(__v); __bin._M_address = NULL; __v = ::operator new(sizeof(size_t) * __max_threads); + std::memset(__v, 0, sizeof(size_t) * __max_threads); __bin._M_free = static_cast<size_t*>(__v); - - __v = ::operator new(sizeof(size_t) * __max_threads); + + __v = ::operator new(sizeof(size_t) * __max_threads + + sizeof(_Atomic_word) * __max_threads); + std::memset(__v, 0, (sizeof(size_t) * __max_threads + + sizeof(_Atomic_word) * __max_threads)); __bin._M_used = static_cast<size_t*>(__v); __v = ::operator new(sizeof(__gthread_mutex_t)); @@ -555,12 +582,6 @@ #else { __GTHREAD_MUTEX_INIT_FUNCTION(__bin._M_mutex); } #endif - for (size_t __threadn = 0; __threadn < __max_threads; ++__threadn) - { - __bin._M_first[__threadn] = NULL; - __bin._M_free[__threadn] = 0; - __bin._M_used[__threadn] = 0; - } } } else @@ -729,16 +750,21 @@ { _Bin_record& __bin = _M_bin[__n]; __v = ::operator new(sizeof(_Block_record*) * __max_threads); + std::memset(__v, 0, sizeof(_Block_record*) * __max_threads); __bin._M_first = static_cast<_Block_record**>(__v); __bin._M_address = NULL; __v = ::operator new(sizeof(size_t) * __max_threads); + std::memset(__v, 0, sizeof(size_t) * __max_threads); __bin._M_free = static_cast<size_t*>(__v); - __v = ::operator new(sizeof(size_t) * __max_threads); + __v = ::operator new(sizeof(size_t) * __max_threads + + sizeof(_Atomic_word) * __max_threads); + std::memset(__v, 0, (sizeof(size_t) * __max_threads + + sizeof(_Atomic_word) * __max_threads)); __bin._M_used = static_cast<size_t*>(__v); - + __v = ::operator new(sizeof(__gthread_mutex_t)); __bin._M_mutex = static_cast<__gthread_mutex_t*>(__v); @@ -751,12 +777,6 @@ #else { __GTHREAD_MUTEX_INIT_FUNCTION(__bin._M_mutex); } #endif - for (size_t __threadn = 0; __threadn < __max_threads; ++__threadn) - { - __bin._M_first[__threadn] = NULL; - __bin._M_free[__threadn] = 0; - __bin._M_used[__threadn] = 0; - } } } else
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