[tor-commits] [tor/maint-0.2.4] Check for CPUs more accurartely when ONLN != CONF.

[nickm at torproject.org]

commit 22804c0391f0549356959e1b474c43bfcba1b8cb
Author: Nick Mathewson <nickm at torproject.org>
Date:   Tue Feb 19 02:31:53 2013 -0500

    Check for CPUs more accurartely when ONLN != CONF.
    
    There are two ways to use sysconf to ask about the number of
    CPUs. When we're on a VM, we would sometimes get it wrong by asking
    for the number of total CPUs (say, 64) when we should have been asking
    for the number of CPUs online (say, 1 or 2).
    
    Fix for bug 8002.
---
 changes/bug8002     |    5 +++++
 src/common/compat.c |   29 +++++++++++++++++++++++++++--
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/changes/bug8002 b/changes/bug8002
new file mode 100644
index 0000000..d6e2ff2
--- /dev/null
+++ b/changes/bug8002
@@ -0,0 +1,5 @@
+  o Minor bugfixes:
+    - When autodetecting the number of CPUs, use the number of available
+      CPUs in preferernce to the number of configured CPUs. Inform the
+      user if this reduces the number of avialable CPUs. Fix for bug 8002.
+      Bugfix on 0.2.3.1-alpha.
diff --git a/src/common/compat.c b/src/common/compat.c
index d7ce894..e620653 100644
--- a/src/common/compat.c
+++ b/src/common/compat.c
@@ -2265,8 +2265,33 @@ compute_num_cpus_impl(void)
     return (int)info.dwNumberOfProcessors;
   else
     return -1;
-#elif defined(HAVE_SYSCONF) && defined(_SC_NPROCESSORS_CONF)
-  long cpus = sysconf(_SC_NPROCESSORS_CONF);
+#elif defined(HAVE_SYSCONF)
+#ifdef _SC_NPROCESSORS_CONF
+  long cpus_conf = sysconf(_SC_NPROCESSORS_CONF);
+#else
+  long cpus_conf = -1;
+#endif
+#ifdef _SC_NPROCESSORS_ONLN
+  long cpus_onln = sysconf(_SC_NPROCESSORS_ONLN);
+#else
+  long cpus_onln = -1;
+#endif
+  long cpus = -1;
+
+  if (cpus_conf > 0 && cpus_onln < 0) {
+    cpus = cpus_conf;
+  } else if (cpus_onln > 0 && cpus_conf < 0) {
+    cpus = cpus_onln;
+  } else if (cpus_onln > 0 && cpus_conf > 0) {
+    if (cpus_onln < cpus_conf) {
+      log_notice(LD_GENERAL, "I think we have %ld CPUS, but only %ld of them "
+                 "are available. Telling Tor to only use %ld. You can over"
+                 "ride this with the NumCPUs option",
+                 cpus_conf, cpus_onln, cpus_onln);
+    }
+    cpus = cpus_onln;
+  }
+
   if (cpus >= 1 && cpus < INT_MAX)
     return (int)cpus;
   else