Add virtual mem size when setting RSS limit on Apple platforms.

[fhahn]

Summary

On Apple platforms, RLIMIT_RSS is mapped to RLIMIT_AS [1] and setting
RLIMIT_AS to a value smaller than the current virtual memory size
will fail. To avoid issues, first get the current size of the virtual
memory and add the user requested limit.

[1] https://github.com/apple/darwin-xnu/blob/a1babec6b135d1f35b2590a1990af3c5c5393479/bsd/sys/resource.h

[fhahn]

Using getpid is not supported on all platforms. I'll see if there's a workaround, otherwise we probably have to ignore RLIMIT_RSS for apple platforms.

[fhahn]

I checked again and the earlier failures where caused by a configuration issue. It should be ready for review!

[ab]

tools/timeit.c

347

We don't have to abort if proc_pidinfo fails, but we should be resilient to that. Maybe explicitly initialize task_info to 0 first? If you can't because it's opaque, I guess you do have to check for success after all ;)

[fhahn]

Zero initialze struct.

[fhahn]

tools/timeit.c

347

Good point, I updated the code to zero initialize the struct.

[fhahn]

I did some more testing and for some benchmarks the provided default value by llvm-lit is too small. Bumping the default is not straigth-forward, as on other platforms rlim_t may only be a unsigned long. And timeit uses atoi to parse the argument value. I don't think this is worth all the trouble and for now I just committed a change ignoring RLIMIT_RSS on Apple platforms (916fce4cbbfd) so the test-suite can be run again on Apple platforms that more strictly enforce the virtual memory limit.

tools/timeit.c

 #include <errno.h>
 #include <signal.h>
 #include <unistd.h>
 
 #include <sys/resource.h>
 #include <sys/time.h>
 #include <sys/wait.h>
 
+#if defined(__APPLE__)
+#include <sys/proc_info.h>
+#endif
+
 /* Enumeration for our exit status codes. */
 enum ExitCode {
   /* \brief Indicates a failure monitoring the target. */
   EXITCODE_MONITORING_FAILURE = 66,
 
   /* \brief Indicates a failure in exec() which usually means an invalid program
    * name. */
   EXITCODE_EXEC_FAILURE = 67,
if (g_target_cpu_limit != ~(rlim_t) 0) {
     set_resource_limit(RLIMIT_CPU, g_target_cpu_limit);
   }
   if (g_target_stack_size_limit != ~(rlim_t) 0) {
     set_resource_limit(RLIMIT_STACK, g_target_stack_size_limit);
   }
   if (g_target_data_size_limit != ~(rlim_t) 0) {
     set_resource_limit(RLIMIT_DATA, g_target_data_size_limit);
   }
+
   if (g_target_rss_size_limit != ~(rlim_t) 0) {
+#if defined(__APPLE__)
+    // On Apple platforms, RLIMIT_RSS is mapped to RLIMIT_AS and setting
+    // RLIMIT_AS to a value smaller than the current virtual memory size will
+    // fail. To avoid issues, first get the current size of the virtual memory
+    // and add the user requested limit.
+    struct proc_taskinfo task_info = {0};
+    proc_pidinfo(getpid(), PROC_PIDTASKINFO, 0, &task_info, sizeof(task_info));
+    g_target_rss_size_limit += task_info.pti_virtual_size;
+#endif
     set_resource_limit(RLIMIT_RSS, g_target_rss_size_limit);
   }
   if (g_target_file_size_limit != ~(rlim_t) 0) {
     set_resource_limit(RLIMIT_FSIZE, g_target_file_size_limit);
   }
   if (g_target_core_limit != ~(rlim_t) 0) {
     set_resource_limit(RLIMIT_CORE, g_target_core_limit);
   }