1 files changed, 136 insertions, 0 deletions
diff --git a/src/support/cond_auto.c b/src/support/cond_auto.c
new file mode 100644
index 00000000000..ec95622f333
--- /dev/null
+++ b/src/support/cond_auto.c
@@ -0,0 +1,136 @@
+/*-
+ * Public Domain 2014-2016 MongoDB, Inc.
+ * Public Domain 2008-2014 WiredTiger, Inc.
+ *
+ * This is free and unencumbered software released into the public domain.
+ *
+ * Anyone is free to copy, modify, publish, use, compile, sell, or
+ * distribute this software, either in source code form or as a compiled
+ * binary, for any purpose, commercial or non-commercial, and by any
+ * means.
+ *
+ * In jurisdictions that recognize copyright laws, the author or authors
+ * of this software dedicate any and all copyright interest in the
+ * software to the public domain. We make this dedication for the benefit
+ * of the public at large and to the detriment of our heirs and
+ * successors. We intend this dedication to be an overt act of
+ * relinquishment in perpetuity of all present and future rights to this
+ * software under copyright law.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include "wt_internal.h"
+
+/*
+ * This is an implementation of condition variables that automatically adjust
+ * the wait time depending on whether the wake is resulting in useful work.
+ */
+
+/*
+ * __wt_cond_auto_alloc --
+ *	Allocate and initialize an automatically adjusting condition variable.
+ */
+int
+__wt_cond_auto_alloc(
+    WT_SESSION_IMPL *session, const char *name,
+    bool is_signalled, uint64_t min, uint64_t max, WT_CONDVAR **condp)
+{
+	WT_CONDVAR *cond;
+
+	WT_RET(__wt_cond_alloc(session, name, is_signalled, condp));
+	cond = *condp;
+
+	cond->min_wait = min;
+	cond->max_wait = max;
+	cond->prev_wait = min;
+
+	return (0);
+}
+
+/*
+ * __wt_cond_auto_signal --
+ *	Signal a condition variable.
+ */
+int
+__wt_cond_auto_signal(WT_SESSION_IMPL *session, WT_CONDVAR *cond)
+{
+
+	WT_ASSERT(session, cond->min_wait != 0);
+	return (__wt_cond_signal(session, cond));
+}
+
+/*
+ * __wt_cond_auto_wait_signal --
+ *	Wait on a mutex, optionally timing out.  If we get it before the time
+ *	out period expires, let the caller know.
+ *	TODO: Can this version of the API be removed, now that we have the
+ *	auto adjusting condition variables?
+ */
+int
+__wt_cond_auto_wait_signal(
+    WT_SESSION_IMPL *session, WT_CONDVAR *cond, bool progress, bool *signalled)
+{
+	uint64_t delta;
+
+	/*
+	 * Catch cases where this function is called with a condition variable
+	 * that was initialized non-auto.
+	 */
+	WT_ASSERT(session, cond->min_wait != 0);
+
+	WT_STAT_FAST_CONN_INCR(session, cond_auto_wait);
+	if (progress)
+		cond->prev_wait = cond->min_wait;
+	else {
+		delta = WT_MAX(1, (cond->max_wait - cond->min_wait) / 10);
+		cond->prev_wait = WT_MIN(
+		    cond->max_wait, cond->prev_wait + delta);
+	}
+
+	WT_RET(__wt_cond_wait_signal(
+	    session, cond, cond->prev_wait, signalled));
+
+	if (progress || *signalled)
+		WT_STAT_FAST_CONN_INCR(session, cond_auto_wait_reset);
+	if (*signalled)
+		cond->prev_wait = cond->min_wait;
+
+	return (0);
+}
+
+/*
+ * __wt_cond_auto_wait --
+ *	Wait on a mutex, optionally timing out.  If we get it before the time
+ *	out period expires, let the caller know.
+ */
+int
+__wt_cond_auto_wait(
+    WT_SESSION_IMPL *session, WT_CONDVAR *cond, bool progress)
+{
+	bool signalled;
+
+	/*
+	 * Call the signal version so the wait period is reset if the
+	 * condition is woken explicitly.
+	 */
+	WT_RET(__wt_cond_auto_wait_signal(session, cond, progress, &signalled));
+
+	return (0);
+}
+
+/*
+ * __wt_cond_auto_destroy --
+ *	Destroy a condition variable.
+ */
+int
+__wt_cond_auto_destroy(WT_SESSION_IMPL *session, WT_CONDVAR **condp)
+{
+	return (__wt_cond_destroy(session, condp));
+}