From 519fc4209460f28de8d4954c1a50402d4af6b02b Mon Sep 17 00:00:00 2001
From: Henning Baldersheim <balder@yahoo-inc.com>
Date: Thu, 11 Feb 2021 23:44:23 +0000
Subject: Use small buffers where size matters more than speed.

---
 jrt/src/com/yahoo/jrt/Supervisor.java             | 12 ++++++++++++
 jrt/src/com/yahoo/jrt/slobrok/api/Mirror.java     |  1 +
 jrt/src/com/yahoo/jrt/slobrok/server/Slobrok.java |  2 +-
 3 files changed, 14 insertions(+), 1 deletion(-)

(limited to 'jrt/src/com')

diff --git a/jrt/src/com/yahoo/jrt/Supervisor.java b/jrt/src/com/yahoo/jrt/Supervisor.java
index d4168e97743..ed94adcadd1 100644
--- a/jrt/src/com/yahoo/jrt/Supervisor.java
+++ b/jrt/src/com/yahoo/jrt/Supervisor.java
@@ -15,6 +15,8 @@ import java.util.concurrent.atomic.AtomicReference;
  **/
 public class Supervisor {
 
+    private static final int SMALL_INPUT_BUFFER_SIZE = 20 * 1024;  // Large enough too hold the typical application buffersize of 17k.
+    private static final int SMALL_OUTPUT_BUFFER_SIZE = 8 *1024;   // Suitable small buffer usage with many connections and little traffic.
     private final Transport         transport;
     private SessionHandler          sessionHandler = null;
     private final Object            methodMapLock = new Object();
@@ -33,6 +35,16 @@ public class Supervisor {
         new MandatoryMethods(this);
     }
 
+    /**
+     * Will optimize buffers size for small memory footprint
+     * Use this when you have many connections with very little traffic.
+     **/
+    public Supervisor enableSmallBuffers() {
+        setMaxInputBufferSize(SMALL_INPUT_BUFFER_SIZE);
+        setMaxOutputBufferSize(SMALL_OUTPUT_BUFFER_SIZE);
+        return this;
+    }
+
     /**
      * Set maximum input buffer size. This value will only affect
      * connections that use a common input buffer when decoding
diff --git a/jrt/src/com/yahoo/jrt/slobrok/api/Mirror.java b/jrt/src/com/yahoo/jrt/slobrok/api/Mirror.java
index 5a4a79995d8..6bceb7a1db0 100644
--- a/jrt/src/com/yahoo/jrt/slobrok/api/Mirror.java
+++ b/jrt/src/com/yahoo/jrt/slobrok/api/Mirror.java
@@ -57,6 +57,7 @@ public class Mirror implements IMirror {
      **/
     public Mirror(Supervisor orb, SlobrokList slobroks, BackOffPolicy bop) {
         this.orb = orb;
+        orb.enableSmallBuffers();
         this.slobroks = slobroks;
         this.backOff = bop;
         transportThread = orb.transport().selectThread();
diff --git a/jrt/src/com/yahoo/jrt/slobrok/server/Slobrok.java b/jrt/src/com/yahoo/jrt/slobrok/server/Slobrok.java
index f19779732ba..1a0c94b9bd0 100644
--- a/jrt/src/com/yahoo/jrt/slobrok/server/Slobrok.java
+++ b/jrt/src/com/yahoo/jrt/slobrok/server/Slobrok.java
@@ -39,7 +39,7 @@ public class Slobrok {
 
     public Slobrok(int port) throws ListenFailedException {
         // NB: rpc must be single-threaded
-        orb = new Supervisor(new Transport("slobrok-" + port, 1));
+        orb = new Supervisor(new Transport("slobrok-" + port, 1)).enableSmallBuffers();
         registerMethods();
         try {
             listener = orb.listen(new Spec(port));
-- 
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