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This displays the page fault count before and after allocating an 40960 byte chunk of memory from a heap, then freeing it and allocating it again.

#! perl -slw use strict; use Inline C => Config => LIBS => '-lpsapi.lib'; use Inline C => 'DATA', NAME => 'heap', CLEAN_AFTER_BUILD => 0; my $heap = heapCreate( 0, 0, 1024 * 1024 ); my $space = heapAlloc( $heap, 0, 4096 * 10 ); heapFree( $heap, 0, $space ); $space = heapAlloc( $heap, 0, 4096 * 10 ); print heapSize( $heap, 0, $space ); __DATA__ __C__ #include <windows.h> #include <psapi.h> U32 heapCreate( U32 flags, U32 initial, int max ) { return (U32) HeapCreate( flags, initial, max ); } U32 heapAlloc( U32 hHeap, U32 flags, U32 size ) { U32 pMem; PROCESS_MEMORY_COUNTERS pmc; pmc.cb = sizeof( PROCESS_MEMORY_COUNTERS ); GetProcessMemoryInfo( GetCurrentProcess(), &pmc, sizeof( PROCESS_MEMORY_COUNTERS ) ); printf( "pagefaults before alloc of %d bytes: %d\n", size, pmc.PageFaultCount ); pMem = (U32)HeapAlloc( (HANDLE)hHeap, flags, (SIZE_T)size ); GetProcessMemoryInfo( GetCurrentProcess(), &pmc, sizeof( PROCESS_MEMORY_COUNTERS ) ); printf( "pagefaults after alloc of %d bytes: %d\n", size, pmc.PageFaultCount ); return pMem; } U32 heapSize( U32 hHeap, U32 flags, U32 mem ) { return (U32)HeapSize( (HANDLE)hHeap, flags, (LPVOID)mem ); } U32 heapFree( U32 hHeap, U32 flags, U32 mem ) { return (U32)HeapFree( (HANDLE)hHeap, flags, (LPVOID)mem ); }

The output

c:\test>HeapMem.pl pagefaults before alloc of 40960 bytes: 952 pagefaults after alloc of 40960 bytes: 964 pagefaults before alloc of 40960 bytes: 964 pagefaults after alloc of 40960 bytes: 964 40960 c:\test>HeapMem.pl pagefaults before alloc of 40960 bytes: 953 pagefaults after alloc of 40960 bytes: 965 pagefaults before alloc of 40960 bytes: 965 pagefaults after alloc of 40960 bytes: 965 40960 c:\test>HeapMem.pl pagefaults before alloc of 40960 bytes: 953 pagefaults after alloc of 40960 bytes: 965 pagefaults before alloc of 40960 bytes: 965 pagefaults after alloc of 40960 bytes: 965 40960

Shows that the first time, allocating 10 pages of memory results in 12 page faults. The second time none.


Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
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In reply to Re^5: RFC: Abusing "virtual" memory (page faults vs malloc) by BrowserUk
in thread RFC: Abusing "virtual" memory by sundialsvc4

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