Merge branch 'teor_ticket24681_028' into maint-0.2.9

diff --cc doc/tor.1.txt
Simple merge

diff --cc src/or/config.c
index ddf49b037e041c06bf8c4bd0ef7334e69ede9e9b,dd0016f7a4260b88f31551347e26f272dcc0c5c9..42ff25877e78853bd718dd97fcf78683afd53786
--- 1/src/or/config.c
--- 2/src/or/config.c
+++ b/src/or/config.c
@@@ -226,10 -225,17 +226,17 @@@ static config_var_t option_vars_[] = 
    VAR("DirReqStatistics",        BOOL,     DirReqStatistics_option, "1"),
    VAR("DirAuthority",            LINELIST, DirAuthorities, NULL),
    V(DirCache,                    BOOL,     "1"),
-   V(DirAuthorityFallbackRate,    DOUBLE,   "1.0"),
+   /* A DirAuthorityFallbackRate of 0.1 means that 0.5% of clients try an
+    * authority when all fallbacks are up, and 2% try an authority when 25% of
+    * fallbacks are down. (We rebuild the list when 25% of fallbacks are down).
+    *
+    * We want to reduce load on authorities, but keep these two figures within
+    * an order of magnitude, so there isn't too much load shifting to
+    * authorities when fallbacks go down. */
+   V(DirAuthorityFallbackRate,    DOUBLE,   "0.1"),
    V(DisableAllSwap,              BOOL,     "0"),
    V(DisableDebuggerAttachment,   BOOL,     "1"),
 -  V(DisableIOCP,                 BOOL,     "1"),
 +  OBSOLETE("DisableIOCP"),
    OBSOLETE("DisableV2DirectoryInfo_"),
    OBSOLETE("DynamicDHGroups"),
    VPORT(DNSPort,                     LINELIST, NULL),