Hi all, The following program: ===================== $ cat p.c #include <sys/mman.h> int main() {  void *t = mmap(0, 0x00000fffffffffffUL, PROT_READ| PROT_WRITE, MAP_ANON | MAP_PRIVATE | MAP_NORESERVE, -1, 0); } ===================== runs for half a second on my 64-bit Snow Leopard machine: ===================== $ time ./p real    0m0.545s user    0m0.000s sys     0m0.544s ===================== According to Shark, most of the time is spent in pmap_remove at exit time: ===================== # Report 5 - session_008.mshark - Time Profile of PID #98012 SharkProfileViewer # Generated from the visible portion of the outline view + 59.9%, pmap_remove, mach_kernel | + 59.9%, vm_map_lookup_locked, mach_kernel | | + 59.9%, vm_map_remove, mach_kernel | | | + 59.9%, task_terminate_internal, mach_kernel | | | | + 59.9%, exit1, mach_kernel | | | | | + 59.9%, exit, mach_kernel | | | | | |   59.9%, unix_syscall64, mach_kernel - 12.0%, pmap64_pde, mach_kernel - 10.7%, pmap64_pdpt, mach_kernel - 5.0%, vm_map_lookup_locked, mach_kernel - 2.7%, zalloc_canblock, mach_kernel - 2.2%, pmap_pde, mach_kernel - 1.8%, lck_mtx_lock_spin, mach_kernel - 1.6%, vm_map_entry_insert, mach_kernel - 1.0%, lck_mtx_unlock_darwin10, mach_kernel - 0.5%, hw_lock_to, mach_kernel ===================== This surprises me, because I thought that a process teardown should be rather cheap (it actually is on Linux). Is it possible to somehow help the kernel with that from the userspace? Rationale: AddressSanitizer (http://code.google.com/p/address-sanitizer/), an LLVM-based tool for memory bugs detection, maps such a huge amount of memory to shadow the address space of the process being debugged. For large applications (like Chrome or WebKit) the virtual page table lookups are not noticeable at all. But our test suite that runs hundreds of tests each doing a fork+exec one by one is very slow because of that. TIA, Alexander Potapenko Software Engineer Google Moscow -- Alexander Potapenko Software Engineer Google Moscow _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app... This email sent to site_archiver@lists.apple.com