From 3e527b9df0d9eb7a42b3fa05745224f00fcb9e19 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Thu, 20 Apr 2017 09:01:09 +0200
Subject: Don't commit all available RAM to VM

---
 bbot/machine.cxx | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/bbot/machine.cxx b/bbot/machine.cxx
index cb835bd..db596cd 100644
--- a/bbot/machine.cxx
+++ b/bbot/machine.cxx
@@ -166,6 +166,20 @@ namespace bbot
     //
     // 2. echo system_powerdown | socat - UNIX-CONNECT:.../monitor
     //
+
+    // We probably don't want to commit all the available RAM to the VM since
+    // some of it could be used on the host side for caching, etc. So the
+    // heuristics that we will use is 4G or 1G per CPU, whichever is greater
+    // and the rest divide equally between the host and the VM.
+    //
+    size_t cpu (ops.cpu ());
+    size_t ram ((cpu < 4 ? 4 : cpu) * 1024 * 1024); // Kb.
+
+    if (ram > ops.ram ())
+      ram = ops.ram ();
+    else
+      ram += (ops.ram () - ram) / 2;
+
     proc = run_io_start (
       trace,
       fdnull (),
@@ -178,9 +192,9 @@ namespace bbot
       //
       // Machine.
       //
-      "-m",   to_string (ops.ram () / 1024) + "M",
+      "-m",   to_string (ram / 1024) + "M",
       "-cpu", "host",
-      "-smp", ops.cpu (),
+      "-smp", cpu,
       //
       // Network.
       //
-- 
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