In my program, I use tcmalloc for memory allocation and release. In order to keep the memory back to the memory in time, after the completion of the call, using** MallocExtension::instance()->ReleaseFreeMemory()**. However, this only ensures that real memory is freed and virtual memory is still occupied.
My program needs to mount a file to a specified memory address through shmat after a series of operations. If tcmalloc uses too much virtual memory, the mount address may become unavailable.
Is there a way to free virtual memory in tcmalloc, or is there a function available in Linux?
int main() {
int i = 0;
while (i < 100) {
char* a = (char*)malloc(1024 * 1024 * 2 * i);
malloc_stats();
free(a);
MallocExtension::instance()->ReleaseFreeMemory();
malloc_stats();
i++;
usleep(1000 * 300);
}
// in last loop , actual memory used is small , but Virtual address space used is big...
// if now I use shmat to mount something, it maybe fail.
return 0;
}
MALLOC: 207634928 ( 198.0 MiB) Bytes in use by application
MALLOC: + 0 ( 0.0 MiB) Bytes in page heap freelist
MALLOC: + 56408 ( 0.1 MiB) Bytes in central cache freelist
MALLOC: + 0 ( 0.0 MiB) Bytes in transfer cache freelist
MALLOC: + 440 ( 0.0 MiB) Bytes in thread cache freelists
MALLOC: + 11251864 ( 10.7 MiB) Bytes in malloc metadata
MALLOC: ------------
MALLOC: = 218943640 ( 208.8 MiB) Actual memory used (physical + swap)
MALLOC: + 10130219008 ( 9660.9 MiB) Bytes released to OS (aka unmapped)
MALLOC: ------------
MALLOC: = 10349162648 ( 9869.7 MiB) **Virtual address space used**
I tried to use MallocExtension::instance()->ReleaseFreeMemory() , but it only frees actual memory, but for virtual address. I hope the virtual addresses are also released.
