From 1047bc110cfda2f4433d2c099c1fb4bd9ee1a6a2 Mon Sep 17 00:00:00 2001
From: Nick Zavaritsky <mejedi@gmail.com>
Date: Thu, 27 Aug 2015 21:54:59 +0300
Subject: [PATCH] gh-885: Trim thread pool once recovery ends
---
src/box/box.cc | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/src/box/box.cc b/src/box/box.cc
index 3288794d37..4a8bfd406e 100644
--- a/src/box/box.cc
+++ b/src/box/box.cc
@@ -607,6 +607,25 @@ engine_init()
engine_register(sophia);
}
+/**
+ * @brief Reduce the current number of threads in the thread pool to the
+ * bare minimum. Doesn't prevent the pool from spawning new threads later
+ * if demand mounts.
+ */
+static void
+thread_pool_trim()
+{
+ /*
+ * Trim OpenMP thread pool.
+ * Though we lack the direct control the workaround below works for
+ * GNU OpenMP library. The library stops surplus threads on entering
+ * a parallel region. Can't go below 2 threads due to the
+ * implementation quirk.
+ */
+#pragma omp parallel num_threads(2)
+ ;
+}
+
static inline void
box_init(void)
{
@@ -677,6 +696,11 @@ box_init(void)
engine_end_recovery();
+ /*
+ * Recovery inflates the thread pool quite a bit (due to parallel sort).
+ */
+ thread_pool_trim();
+
rmean_cleanup(rmean_box);
if (recovery_has_replica(recovery))
--
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