[or-cvs] r17690: {tor} Replace calls to time(NULL) that occur on the order of once (in tor/trunk: . doc src/common src/or)
nickm at seul.org
nickm at seul.org
Thu Dec 18 17:19:18 UTC 2008
Author: nickm
Date: 2008-12-18 12:19:04 -0500 (Thu, 18 Dec 2008)
New Revision: 17690
Modified:
tor/trunk/ChangeLog
tor/trunk/doc/TODO.021
tor/trunk/src/common/util.c
tor/trunk/src/common/util.h
tor/trunk/src/or/connection.c
tor/trunk/src/or/connection_edge.c
tor/trunk/src/or/main.c
tor/trunk/src/or/relay.c
tor/trunk/src/or/test.c
Log:
Replace calls to time(NULL) that occur on the order of once per read, one per write, or once per cell with calls to a function that looks at a cached value of time. This is tricksy to benchmark, since it will only help on systems where time() is a syscall and syscalls are relatively slow.
Modified: tor/trunk/ChangeLog
===================================================================
--- tor/trunk/ChangeLog 2008-12-18 17:18:14 UTC (rev 17689)
+++ tor/trunk/ChangeLog 2008-12-18 17:19:04 UTC (rev 17690)
@@ -43,6 +43,9 @@
- On platforms with a maximum syslog string length, truncate syslog
messages to that length ourselves, rather than relying on the
system to do it for us.
+ - Optimize out calls to time(NULL) that occur for every IO operation, or
+ for every cell. On systems where time() is a slow syscalls, this will
+ be slightly helpful.
o Minor features (controller):
- New CONSENSUS_ARRIVED event to note when a new consensus has
Modified: tor/trunk/doc/TODO.021
===================================================================
--- tor/trunk/doc/TODO.021 2008-12-18 17:18:14 UTC (rev 17689)
+++ tor/trunk/doc/TODO.021 2008-12-18 17:19:04 UTC (rev 17690)
@@ -362,7 +362,7 @@
"who can change what" in local_routerstatus explicit. Make
local_routerstatus (or equivalent) subsume all places to go for "what
router is this?"
- - Don't call time(NULL) so much; instead have a static time_t field
+ o Don't call time(NULL) so much; instead have a static time_t field
that gets updated only a handful of times per second.
- Refactor unit tests into multiple files
Modified: tor/trunk/src/common/util.c
===================================================================
--- tor/trunk/src/common/util.c 2008-12-18 17:18:14 UTC (rev 17689)
+++ tor/trunk/src/common/util.c 2008-12-18 17:19:04 UTC (rev 17690)
@@ -1285,8 +1285,39 @@
}
/* =====
+ * Cached time
+ * ===== */
+
+#ifndef TIME_IS_FAST
+/** Cached estimate of the currrent time. Updated around once per second;
+ * may be a few seconds off if we are really busy. This is a hack to avoid
+ * calling time(NULL) (which not everybody has optimized) on critical paths.
+ */
+static time_t cached_approx_time = 0;
+
+/** Return a cached estimate of the current time from when
+ * update_approx_time() was last called. This is a hack to avoid calling
+ * time(NULL) on critical paths: please do not even think of calling it
+ * anywhere else. */
+time_t
+approx_time(void)
+{
+ return cached_approx_time;
+}
+
+/** Update the cached estimate of the current time. This function SHOULD be
+ * called once per second, and MUST be called before the first call to
+ * get_approx_time. */
+void
+update_approx_time(time_t now)
+{
+ cached_approx_time = now;
+}
+#endif
+
+/* =====
* Fuzzy time
- * XXXX022 Use this consistently or rip it out.
+ * XXXX022 Use this consistently or rip most of it out.
* ===== */
/* In a perfect world, everybody would run ntp, and ntp would be perfect, so
Modified: tor/trunk/src/common/util.h
===================================================================
--- tor/trunk/src/common/util.h 2008-12-18 17:18:14 UTC (rev 17689)
+++ tor/trunk/src/common/util.h 2008-12-18 17:19:04 UTC (rev 17690)
@@ -213,6 +213,16 @@
int parse_iso_time(const char *buf, time_t *t);
int parse_http_time(const char *buf, struct tm *tm);
int format_time_interval(char *out, size_t out_len, long interval);
+
+/* Cached time */
+#ifdef TIME_IS_FAST
+#define approx_time() time(NULL)
+#define update_approx_time(t) STMT_NIL
+#else
+time_t approx_time(void);
+void update_approx_time(time_t now);
+#endif
+
/* Fuzzy time. */
void ftime_set_maximum_sloppiness(int seconds);
void ftime_set_estimated_skew(int seconds);
Modified: tor/trunk/src/or/connection.c
===================================================================
--- tor/trunk/src/or/connection.c 2008-12-18 17:18:14 UTC (rev 17689)
+++ tor/trunk/src/or/connection.c 2008-12-18 17:19:04 UTC (rev 17690)
@@ -1724,7 +1724,7 @@
if (global_read_bucket <= 0) {
reason = "global read bucket exhausted. Pausing.";
- } else if (connection_counts_as_relayed_traffic(conn, time(NULL)) &&
+ } else if (connection_counts_as_relayed_traffic(conn, approx_time()) &&
global_relayed_read_bucket <= 0) {
reason = "global relayed read bucket exhausted. Pausing.";
} else if (connection_speaks_cells(conn) &&
@@ -1748,7 +1748,7 @@
if (global_write_bucket <= 0) {
reason = "global write bucket exhausted. Pausing.";
- } else if (connection_counts_as_relayed_traffic(conn, time(NULL)) &&
+ } else if (connection_counts_as_relayed_traffic(conn, approx_time()) &&
global_relayed_write_bucket <= 0) {
reason = "global relayed write bucket exhausted. Pausing.";
#if 0
@@ -1928,7 +1928,7 @@
if (conn->marked_for_close)
return 0; /* do nothing */
- conn->timestamp_lastread = time(NULL);
+ conn->timestamp_lastread = approx_time();
switch (conn->type) {
case CONN_TYPE_OR_LISTENER:
@@ -1994,7 +1994,7 @@
if (n_read) {
/* Probably a no-op, but hey. */
- connection_buckets_decrement(linked, time(NULL), 0, n_read);
+ connection_buckets_decrement(linked, approx_time(), 0, n_read);
if (connection_flushed_some(linked) < 0)
connection_mark_for_close(linked);
@@ -2034,8 +2034,7 @@
if (at_most == -1) { /* we need to initialize it */
/* how many bytes are we allowed to read? */
- /* XXXX021 too many calls to time(). Do they hurt? */
- at_most = connection_bucket_read_limit(conn, time(NULL));
+ at_most = connection_bucket_read_limit(conn, approx_time());
}
slack_in_buf = buf_slack(conn->inbuf);
@@ -2155,7 +2154,7 @@
edge_conn->n_read += (int)n_read;
}
- connection_buckets_decrement(conn, time(NULL), n_read, n_written);
+ connection_buckets_decrement(conn, approx_time(), n_read, n_written);
if (more_to_read && result == at_most) {
slack_in_buf = buf_slack(conn->inbuf);
@@ -2223,7 +2222,7 @@
socklen_t len=(socklen_t)sizeof(e);
int result;
ssize_t max_to_write;
- time_t now = time(NULL);
+ time_t now = approx_time();
size_t n_read = 0, n_written = 0;
tor_assert(!connection_is_listener(conn));
@@ -2350,7 +2349,7 @@
edge_conn->n_written += (int)n_written;
}
- connection_buckets_decrement(conn, time(NULL), n_read, n_written);
+ connection_buckets_decrement(conn, approx_time(), n_read, n_written);
if (result > 0) {
/* If we wrote any bytes from our buffer, then call the appropriate
Modified: tor/trunk/src/or/connection_edge.c
===================================================================
--- tor/trunk/src/or/connection_edge.c 2008-12-18 17:18:14 UTC (rev 17689)
+++ tor/trunk/src/or/connection_edge.c 2008-12-18 17:19:04 UTC (rev 17690)
@@ -2159,7 +2159,7 @@
uint32_t a;
size_t len = strlen(ap_conn->socks_request->address);
char c = 0;
- /* XXXX021 This logic is a little ugly: we check for an in-addr.arpa ending
+ /* XXXX This logic is a little ugly: we check for an in-addr.arpa ending
* on the address. If we have one, the address is already in the right
* order, so we'll leave it alone later. Otherwise, we reverse it and
* turn it into an in-addr.arpa address. */
Modified: tor/trunk/src/or/main.c
===================================================================
--- tor/trunk/src/or/main.c 2008-12-18 17:18:14 UTC (rev 17689)
+++ tor/trunk/src/or/main.c 2008-12-18 17:19:04 UTC (rev 17690)
@@ -1192,6 +1192,7 @@
/* log_fn(LOG_NOTICE, "Tick."); */
tor_gettimeofday(&now);
+ update_approx_time(now.tv_sec);
/* the second has rolled over. check more stuff. */
bytes_written = stats_prev_global_write_bucket - global_write_bucket;
@@ -1461,6 +1462,8 @@
event_active(conn->read_event, EV_READ, 1));
called_loop_once = smartlist_len(active_linked_connection_lst) ? 1 : 0;
+ update_approx_time(time(NULL));
+
/* poll until we have an event, or the second ends, or until we have
* some active linked connections to trigger events for. */
loop_result = event_loop(called_loop_once ? EVLOOP_ONCE : 0);
@@ -2059,6 +2062,7 @@
tor_main(int argc, char *argv[])
{
int result = 0;
+ update_approx_time(time(NULL));
tor_threads_init();
init_logging();
#ifdef USE_DMALLOC
Modified: tor/trunk/src/or/relay.c
===================================================================
--- tor/trunk/src/or/relay.c 2008-12-18 17:18:14 UTC (rev 17689)
+++ tor/trunk/src/or/relay.c 2008-12-18 17:19:04 UTC (rev 17690)
@@ -505,8 +505,7 @@
if (cell_direction == CELL_DIRECTION_OUT && circ->n_conn) {
/* if we're using relaybandwidthrate, this conn wants priority */
- /* XXXX021 the call to time() seems little too frequent */
- circ->n_conn->client_used = time(NULL);
+ circ->n_conn->client_used = approx_time();
}
if (cell_direction == CELL_DIRECTION_OUT) {
@@ -1840,7 +1839,7 @@
* get called, and we can start putting more data onto the buffer then.
*/
log_debug(LD_GENERAL, "Primed a buffer.");
- connection_or_flush_from_first_active_circuit(orconn, 1, time(NULL));
+ connection_or_flush_from_first_active_circuit(orconn, 1, approx_time());
}
}
Modified: tor/trunk/src/or/test.c
===================================================================
--- tor/trunk/src/or/test.c 2008-12-18 17:18:14 UTC (rev 17689)
+++ tor/trunk/src/or/test.c 2008-12-18 17:19:04 UTC (rev 17690)
@@ -4538,6 +4538,7 @@
}
#endif
+ update_approx_time(time(NULL));
options = options_new();
tor_threads_init();
init_logging();
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