Snippet: Enable Low Fragmentation Heap for all heaps
Monday, February 23rd, 2009The following code is a code snippet that enable the Low Fragmentation Heap for all heaps. Remembers that a process has at last one heap but for example a CRT console application has practically at last two heaps. The first heap is default heap of process and the second is the CRT heap. If you use a lot of external DLLs is very common that one of this DLL allocate a private heap.
1: // code snippet that try to enable LFH for all heaps of your runnig program.
2: HANDLE* hHeaps = NULL;
3: int numHeap = GetProcessHeaps(0, NULL);
4: if(numHeap > 0)
5: {
6: ULONG ulEnableLFH = 2;
7: hHeaps = (HANDLE*)malloc(sizeof(HANDLE)*numHeap);
8: if(GetProcessHeaps(numHeap, hHeaps) == numHeap)
9: {
10: for(int i = 0; i < numHeap; i++)
11: {
12: if(!HeapSetInformation(hHeaps[i], HeapCompatibilityInformation, &ulEnableLFH, sizeof(ulEnableLFH)))
13: {
14: printf("Failed to enable LFH for heap %d.", i);
15: }
16: }
17: }
18: else
19: {
20: // quite strange !!!
21: }
22: free(hHeaps);
23: }
Suggested reading Windows Internals 4th edition for more details.