[PATCH v2 08/11] vinyl: do not try to trigger dump in regulator if already in progress

[Vladimir Davydov <vdavydov.dev@gmail.com>]

This is pointless since trigger_dump_cb callback will return right away
in such a case. Let's wrap trigger_dump_cb in vy_regulator_trigger_dump
method, which will actulally invoke the callback only if the previous
dump has already completed (i.e. vy_regulator_dump_complete was called).

This also gives us a definite place in code where we can adjust the rate
limit so as to guarantee that a triggered memory dump will finish before
we hit the hard memory limit (this will be done later).

Needed for #1862
---
 src/box/vinyl.c        |  5 +++--
 src/box/vy_regulator.c | 20 ++++++++++++++++++--
 src/box/vy_regulator.h | 11 +++++++++--
 3 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/src/box/vinyl.c b/src/box/vinyl.c
index 25ba92fe..c3d95777 100644
--- a/src/box/vinyl.c
+++ b/src/box/vinyl.c
@@ -2427,7 +2427,7 @@ vy_env_quota_exceeded_cb(struct vy_quota *quota)
 	vy_regulator_no_memory(&env->regulator);
 }
 
-static void
+static int
 vy_env_trigger_dump_cb(struct vy_regulator *regulator)
 {
 	struct vy_env *env = container_of(regulator, struct vy_env, regulator);
@@ -2439,9 +2439,10 @@ vy_env_trigger_dump_cb(struct vy_regulator *regulator)
 		 * quota has been consumed by pending transactions.
 		 * There's nothing we can do about that.
 		 */
-		return;
+		return -1;
 	}
 	vy_scheduler_trigger_dump(&env->scheduler);
+	return 0;
 }
 
 static void
diff --git a/src/box/vy_regulator.c b/src/box/vy_regulator.c
index 3bd4fee4..5ec5629f 100644
--- a/src/box/vy_regulator.c
+++ b/src/box/vy_regulator.c
@@ -31,6 +31,7 @@
 #include "vy_regulator.h"
 
 #include <math.h>
+#include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <tarantool_ev.h>
@@ -66,6 +67,18 @@ static const int VY_DUMP_BW_PCT = 10;
 static const size_t VY_DUMP_BW_DEFAULT = 10 * 1024 * 1024;
 
 static void
+vy_regulator_trigger_dump(struct vy_regulator *regulator)
+{
+	if (regulator->dump_in_progress)
+		return;
+
+	if (regulator->trigger_dump_cb(regulator) != 0)
+		return;
+
+	regulator->dump_in_progress = true;
+}
+
+static void
 vy_regulator_update_write_rate(struct vy_regulator *regulator)
 {
 	size_t used_curr = regulator->quota->used;
@@ -152,6 +165,7 @@ vy_regulator_create(struct vy_regulator *regulator, struct vy_quota *quota,
 	regulator->watermark = SIZE_MAX;
 	regulator->write_rate = 0;
 	regulator->dump_bw = VY_DUMP_BW_DEFAULT;
+	regulator->dump_in_progress = false;
 }
 
 void
@@ -170,20 +184,22 @@ vy_regulator_destroy(struct vy_regulator *regulator)
 void
 vy_regulator_no_memory(struct vy_regulator *regulator)
 {
-	regulator->trigger_dump_cb(regulator);
+	vy_regulator_trigger_dump(regulator);
 }
 
 void
 vy_regulator_check_watermark(struct vy_regulator *regulator)
 {
 	if (regulator->quota->used >= regulator->watermark)
-		regulator->trigger_dump_cb(regulator);
+		vy_regulator_trigger_dump(regulator);
 }
 
 void
 vy_regulator_dump_complete(struct vy_regulator *regulator,
 			   size_t mem_dumped, double dump_duration)
 {
+	regulator->dump_in_progress = false;
+
 	if (dump_duration > 0) {
 		histogram_collect(regulator->dump_bw_hist,
 				  mem_dumped / dump_duration);
diff --git a/src/box/vy_regulator.h b/src/box/vy_regulator.h
index 9336adc9..0ea708d6 100644
--- a/src/box/vy_regulator.h
+++ b/src/box/vy_regulator.h
@@ -31,6 +31,7 @@
  * SUCH DAMAGE.
  */
 
+#include <stdbool.h>
 #include <stddef.h>
 #include <tarantool_ev.h>
 
@@ -42,7 +43,7 @@ struct histogram;
 struct vy_quota;
 struct vy_regulator;
 
-typedef void
+typedef int
 (*vy_trigger_dump_f)(struct vy_regulator *regulator);
 
 /**
@@ -59,7 +60,7 @@ struct vy_regulator {
 	/**
 	 * Called when the regulator detects that memory usage
 	 * exceeds the computed watermark. Supposed to trigger
-	 * memory dump.
+	 * memory dump and return 0 on success, -1 on failure.
 	 */
 	vy_trigger_dump_f trigger_dump_cb;
 	/**
@@ -100,6 +101,12 @@ struct vy_regulator {
 	 * best result among 10% worst measurements.
 	 */
 	struct histogram *dump_bw_hist;
+	/**
+	 * Set if the last triggered memory dump hasn't completed
+	 * yet, i.e. trigger_dump_cb() was successfully invoked,
+	 * but vy_regulator_dump_complete() hasn't been called yet.
+	 */
+	bool dump_in_progress;
 };
 
 void
-- 
2.11.0