sched: Add Schedulers torrc option

This option is a list of possible scheduler type tor can use ordered by
priority. Its default value is "KIST,KISTLite,Vanilla" which means that KIST
will be used first and if unavailable will fallback to KISTLite and so on.

Signed-off-by: David Goulet <dgoulet@torproject.org>

1 files changed, 38 insertions, 7 deletions

diff --git a/src/or/scheduler_kist.c b/src/or/scheduler_kist.c
index aec8192ed1..8646169ee3 100644
--- a/src/or/scheduler_kist.c
+++ b/src/or/scheduler_kist.c
@@ -26,12 +26,18 @@
  * Data structures and supporting functions
  *****************************************************************************/
 
+#ifdef HAVE_KIST_SUPPORT
+/* Indicate if KIST lite mode is on or off. We can disable it at runtime.
+ * Important to have because of the KISTLite -> KIST possible transition. */
+static unsigned int kist_lite_mode = 0;
 /* Indicate if we don't have the kernel support. This can happen if the kernel
  * changed and it doesn't recognized the values passed to the syscalls needed
  * by KIST. In that case, fallback to the naive approach. */
-#ifdef HAVE_KIST_SUPPORT
 static unsigned int kist_no_kernel_support = 0;
-#endif /* HAVE_KIST_SUPPORT */
+#else
+static unsigned int kist_no_kernel_support = 1;
+static unsigned int kist_lite_mode = 1;
+#endif
 
 /* Socket_table hash table stuff. The socket_table keeps track of per-socket
  * limit information imposed by kist and used by kist. */
@@ -193,7 +199,7 @@ update_socket_info_impl, (socket_table_ent_t *ent))
   struct tcp_info tcp;
   socklen_t tcp_info_len = sizeof(tcp);
 
-  if (kist_no_kernel_support) {
+  if (kist_no_kernel_support || kist_lite_mode) {
     goto fallback;
   }
 
@@ -686,15 +692,40 @@ kist_scheduler_run_interval(const networkstatus_t *ns)
   return run_interval;
 }
 
+/* Set KISTLite mode that is KIST without kernel support. */
+void
+scheduler_kist_set_lite_mode(void)
+{
+  kist_lite_mode = 1;
+  log_info(LD_SCHED,
+           "Setting KIST scheduler without kernel support (KISTLite mode)");
+}
+
+/* Set KIST mode that is KIST with kernel support. */
+void
+scheduler_kist_set_full_mode(void)
+{
+  kist_lite_mode = 0;
+  log_info(LD_SCHED,
+           "Setting KIST scheduler with kernel support (KIST mode)");
+}
+
 #ifdef HAVE_KIST_SUPPORT
 
 /* Return true iff the scheduler subsystem should use KIST. */
 int
-scheduler_should_use_kist(void)
+scheduler_can_use_kist(void)
 {
+  if (kist_no_kernel_support) {
+    /* We have no kernel support so we can't use KIST. */
+    return 0;
+  }
+
+  /* We do have the support, time to check if we can get the interval that the
+   * consensus can be disabling. */
   int64_t run_interval = kist_scheduler_run_interval(NULL);
-  log_info(LD_SCHED, "Determined sched_run_interval should be %" PRId64 ". "
-                     "Will%s use KIST.",
+  log_debug(LD_SCHED, "Determined KIST sched_run_interval should be "
+                      "%" PRId64 ". Can%s use KIST.",
            run_interval, (run_interval > 0 ? "" : " not"));
   return run_interval > 0;
 }
@@ -702,7 +733,7 @@ scheduler_should_use_kist(void)
 #else /* HAVE_KIST_SUPPORT */
 
 int
-scheduler_should_use_kist(void)
+scheduler_can_use_kist(void)
 {
   return 0;
 }