1 files changed, 59 insertions, 0 deletions
diff --git a/src/crimson/common/throttle.cc b/src/crimson/common/throttle.cc
new file mode 100644
index 000000000..bd9195181
--- /dev/null
+++ b/src/crimson/common/throttle.cc
@@ -0,0 +1,59 @@
+#include "throttle.h"
+
+namespace crimson::common {
+
+int64_t Throttle::take(int64_t c)
+{
+  if (!max) {
+    return 0;
+  }
+  count += c;
+  return count;
+}
+
+int64_t Throttle::put(int64_t c)
+{
+  if (!max) {
+    return 0;
+  }
+  if (!c) {
+    return count;
+  }
+  on_free_slots.signal();
+  count -= c;
+  return count;
+}
+
+seastar::future<> Throttle::get(size_t c)
+{
+  if (!max) {
+    return seastar::make_ready_future<>();
+  }
+  return on_free_slots.wait([this, c] {
+    return !_should_wait(c);
+  }).then([this, c] {
+    count += c;
+    return seastar::make_ready_future<>();
+  });
+}
+
+void Throttle::reset_max(size_t m) {
+  if (max == m) {
+    return;
+  }
+
+  if (m > max) {
+    on_free_slots.signal();
+  }
+  max = m;
+}
+
+bool Throttle::_should_wait(size_t c) const {
+  if (!max) {
+    return false;
+  }
+  return ((c <= max && count + c > max) || // normally stay under max
+          (c >= max && count > max));      // except for large c
+}
+
+} // namespace crimson::common