On 1/12/2018 9:33 AM, Corinna Vinschen wrote: > On Jan 12 15:06, Christian Franke wrote: >> Lee wrote: >>> Why is the cygwin gcc calloc so much slower than the >>> i686-w64-mingw32-gcc calloc? >>> 1:12 vs 0:11 >>> >>> $cat calloc-test.c >>> #include <stdio.h> >>> #include <stdlib.h> >>> #define ALLOCATION_SIZE (100 * 1024 * 1024) >>> int main (int argc, char *argv[]) { >>> for (int i = 0; i < 10000; i++) { >>> void *temp = calloc(ALLOCATION_SIZE, 1); >>> if ( temp == NULL ) { >>> printf("drat! calloc returned NULL\n"); >>> return 1; >>> } >>> free(temp); >>> } >>> return 0; >>> } >>> >> >> Could reproduce the difference on an older i7-2600K machine: >> >> Cygwin: ~20s >> MinGW: ~4s >> >> Timing [cm]alloc() calls without actually using the allocated memory might >> produce misleading results due to lazy page allocation and/or zero-filling. >> >> MinGW binaries use calloc() from msvcrt.dll. This calloc() does not call >> malloc() and then memset(). It directly calls: >> >> mem = HeapAlloc(_crtheap, HEAP_ZERO_MEMORY, size); >> >> which possibly only reserves allocate-and-zero-fill-on-demand pages for >> later. >> >> Cygwin's calloc() is different. > > But then again, Cygwin's malloc *is* slow, particulary in > memory-demanding multi-threaded scenarios since that serializes all > malloc/free calls. > > The memory handling within Cygwin is tricky. Attempts to replace good > old dlmalloc with a fresher jemalloc or ptmalloc failed, but that only > means the developer (i.e., me, in case of ptmalloc) was too lazy... > busy! I mean busy... to pull this through. > > Having said that, if somebody would like to take a stab at replacing > dlmalloc with something leaner, I would be very happy and assist as > much as I can.
Corina, how reliable is the Cygwin time function on a non-Cygwin executable? Isn't this a comparison of apples to oranges? -- cyg Simple -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple