Glibc内存管理--ptmalloc2源代码分析（三十二）
5.8.2 _int_free()
/* If freeing a large space, consolidate possibly-surrounding chunks. Then, if the total unused topmost memory exceeds trim threshold, ask malloc_trim to reduce top. Unless max_fast is 0, we don't know if there are fastbins bordering top, so we cannot tell for sure whether threshold has been reached unless fastbins are consolidated. But we don't want to consolidate on each free. As a compromise, consolidation is performed if FASTBIN_CONSOLIDATION_THRESHOLD is reached. */ if ((unsigned long)(size) >= FASTBIN_CONSOLIDATION_THRESHOLD) { if (have_fastchunks(av)) malloc_consolidate(av);如果合并后的chunk大小大于64KB，并且fast bins中存在空闲chunk，调用malloc_consolidate()函数合并fast bins中的空闲chunk到unsorted bin中。 if (av == &main_arena) {#ifndef MORECORE_CANNOT_TRIM if ((unsigned long)(chunksize(av->top)) >= (unsigned long)(mp_.trim_threshold)) sYSTRIm(mp_.top_pad, av);如果当前分配区为主分配区，并且top chunk的大小大于heap的收缩阈值，调用sYSTRIm()函数首先heap。#endif } else { /* Always try heap_trim(), even if the top chunk is not large, because the corresponding heap might go away. */ heap_info *heap = heap_for_ptr(top(av)); assert(heap->ar_ptr == av); heap_trim(heap, mp_.top_pad);如果为非主分配区，调用heap_trim()函数收缩非主分配区的sub_heap。 } }#ifdef ATOMIC_FASTBINS if (! have_lock) { assert (locked); (void)mutex_unlock(&av->mutex); }#endif如果开启了ATOMIC_FASTBINS优化并获得分配区的锁，则对分配区解锁。 } /* If the chunk was allocated via mmap, release via munmap(). Note that if HAVE_MMAP is false but chunk_is_mmapped is true, then user must have overwritten memory. There's nothing we can do to catch this error unless MALLOC_DEBUG is set, in which case check_inuse_chunk (above) will have triggered error. */ else {#if HAVE_MMAPmunmap_chunk (p);如果当前free的chunk是通过mmap()分配的，调用munma_chunk()释放内存。#endif }}?
?
?
?
?
