Autodetect the number of CPUs when possible if NumCPUs==0

This is needed for IOCP, since telling the IOCP backend about all
your CPUs is a good idea.  It'll also come in handy with asn's
multithreaded crypto stuff, and for people who run servers without
reading the manual.

3 files changed, 18 insertions, 3 deletions

diff --git a/src/or/config.c b/src/or/config.c
index c5b0ccf586..23cad9268b 100644
--- a/src/or/config.c
+++ b/src/or/config.c
@@ -307,7 +307,7 @@ static config_var_t _option_vars[] = {
   V(WarnUnsafeSocks,              BOOL,     "1"),
   V(NoPublish,                   BOOL,     "0"),
   VAR("NodeFamily",              LINELIST, NodeFamilies,         NULL),
-  V(NumCpus,                     UINT,     "1"),
+  V(NumCpus,                     UINT,     "0"),
   V(NumEntryGuards,              UINT,     "3"),
   V(ORListenAddress,             LINELIST, NULL),
   V(ORPort,                      UINT,     "0"),
@@ -4892,6 +4892,19 @@ config_parse_interval(const char *s, int *ok)
   return (int)r;
 }
 
+/** Return the number of cpus configured in <b>options</b>.  If we are
+ * told to auto-detect the number of cpus, return the auto-detected number. */
+int
+get_num_cpus(const or_options_t *options)
+{
+  if (options->NumCpus == 0) {
+    int n = compute_num_cpus();
+    return (n >= 1) ? n : 1;
+  } else {
+    return options->NumCpus;
+  }
+}
+
 /**
  * Initialize the libevent library.
  */
@@ -4913,7 +4926,7 @@ init_libevent(const or_options_t *options)
 
   memset(&cfg, 0, sizeof(cfg));
   cfg.disable_iocp = options->DisableIOCP;
-  cfg.num_cpus = options->NumCpus;
+  cfg.num_cpus = get_num_cpus(options);
 
   tor_libevent_initialize(&cfg);
 
diff --git a/src/or/config.h b/src/or/config.h
index 7a4ba5c60f..bd5827b4e8 100644
--- a/src/or/config.h
+++ b/src/or/config.h
@@ -57,6 +57,8 @@ char *options_get_datadir_fname2_suffix(or_options_t *options,
 #define get_datadir_fname_suffix(sub1, suffix) \
   get_datadir_fname2_suffix((sub1), NULL, (suffix))
 
+int get_num_cpus(const or_options_t *options);
+
 or_state_t *get_or_state(void);
 int or_state_save(time_t now);
 
diff --git a/src/or/cpuworker.c b/src/or/cpuworker.c
index e5b2c71025..cfe9f3af9c 100644
--- a/src/or/cpuworker.c
+++ b/src/or/cpuworker.c
@@ -366,7 +366,7 @@ spawn_cpuworker(void)
 static void
 spawn_enough_cpuworkers(void)
 {
-  int num_cpuworkers_needed = get_options()->NumCpus;
+  int num_cpuworkers_needed = get_num_cpus(get_options());
 
   if (num_cpuworkers_needed < MIN_CPUWORKERS)
     num_cpuworkers_needed = MIN_CPUWORKERS;