rx: Make rx_softAckDelay & rx_lastAckDelay private

The values of these two parameters directly affect the modifiers
that are needed in the peer's RTT calculations, and so can not
arbitrarily be changed by applications.

lastAckDelay has been 400ms since the first OpenAFS release, and
that value is used as a modifier when computing the timeout of the
last packet. It is likely that any change which made this value
longer than 400ms would have detrimental effects on deployed clients

softAckDelay has been 100ms for a similar time period. We have
chopped and changed the value of minPeerTimeout, so it is unclear
what the maximal value for this parameter is. For much of OpenAFS's
life, minPeerTimeout was a 350ms padding value, which suggests that
copying TCP, and setting the maximal value at 200ms would be a safe
option. For now, however, leave it at 100ms to avoid unexpected
side effects.

hardAckDelay is not addressed by this patch set, as all ACK packets
sent from the application thread are marked as delayed, and so
currently have no part in computing RTT times. It is likely, however,
that any changes to the hard ACK timeout should be very carefully
considered.

Change-Id: Ibdeae4577b09d120f22bb922697f92d63aaf0dff
Reviewed-on: http://gerrit.openafs.org/4858
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>

diff --git a/src/rx/rx.c b/src/rx/rx.c
index 89e6df12d888d59154359843d2ab04a16ef19bae..26c0aefee2632bd8dd5d3e6997d795e6669782af 100644 (file)
--- a/src/rx/rx.c
+++ b/src/rx/rx.c
@@ -111,6 +111,25 @@ struct rx_tq_debug {
 } rx_tq_debug;
 #endif /* AFS_GLOBAL_RXLOCK_KERNEL */
 
+/* Constant delay time before sending an acknowledge of the last packet
+ * received.  This is to avoid sending an extra acknowledge when the
+ * client is about to make another call, anyway, or the server is
+ * about to respond.
+ *
+ * The lastAckDelay may not exceeed 400ms without causing peers to
+ * unecessarily timeout.
+ */
+struct clock rx_lastAckDelay = {0, 400000};
+
+/* Constant delay time before sending a soft ack when none was requested.
+ * This is to make sure we send soft acks before the sender times out,
+ * Normally we wait and send a hard ack when the receiver consumes the packet
+ *
+ * This value has been 100ms in all shipping versions of OpenAFS. Changing it
+ * will require changes to the peer's RTT calculations.
+ */
+struct clock rx_softAckDelay = {0, 100000};
+
 /*
  * rxi_rpc_peer_stat_cnt counts the total number of peer stat structures
  * currently allocated within rx.  This number is used to allocate the
@@ -562,12 +581,8 @@ rx_InitHost(u_int host, u_int port)
     rx_connHashTable = (struct rx_connection **)htable;
     rx_peerHashTable = (struct rx_peer **)ptable;
 
-    rx_lastAckDelay.sec = 0;
-    rx_lastAckDelay.usec = 400000;     /* 400 milliseconds */
     rx_hardAckDelay.sec = 0;
     rx_hardAckDelay.usec = 100000;     /* 100 milliseconds */
-    rx_softAckDelay.sec = 0;
-    rx_softAckDelay.usec = 100000;     /* 100 milliseconds */
 
     rxevent_Init(20, rxi_ReScheduleEvents);
 

diff --git a/src/rx/rx_globals.h b/src/rx/rx_globals.h
index 85e62159e1dc9ce7280bbbc803cecd37f0ee9135..3e17c7cb8c4fe2dec9dc2b8e4b7c5b29957792d8 100644 (file)
--- a/src/rx/rx_globals.h
+++ b/src/rx/rx_globals.h
@@ -49,9 +49,6 @@ EXT struct rx_queue rx_incomingCallQueue;
 /* Server processes wait on this queue when there are no appropriate calls to process */
 EXT struct rx_queue rx_idleServerQueue;
 
-/* Constant delay time before sending an acknowledge of the last packet received.  This is to avoid sending an extra acknowledge when the client is about to make another call, anyway, or the server is about to respond. */
-EXT struct clock rx_lastAckDelay;
-
 /* Constant delay time before sending a hard ack if the receiver consumes
  * a packet while no delayed ack event is scheduled. Ensures that the
  * sender is able to advance its window when the receiver consumes a packet
@@ -59,11 +56,6 @@ EXT struct clock rx_lastAckDelay;
  */
 EXT struct clock rx_hardAckDelay;
 
-/* Constant delay time before sending a soft ack when none was requested.
- * This is to make sure we send soft acks before the sender times out,
- * Normally we wait and send a hard ack when the receiver consumes the packet */
-EXT struct clock rx_softAckDelay;
-
 #if defined(RXDEBUG) || defined(AFS_NT40_ENV)
 /* Variable to allow introduction of network unreliability; exported from libafsrpc */
 EXT int rx_intentionallyDroppedPacketsPer100 GLOBALSINIT(0);   /* Dropped on Send */