From a36bd7fbafcd41e91f14c884f7b462c4800bfb8f Mon Sep 17 00:00:00 2001
From: Slava Pestov <slava@slava-pestovs-macbook-pro.local>
Date: Fri, 17 Sep 2010 20:52:27 -0700
Subject: [PATCH] vm: don't keep more than 10 unused contexts around to prevent
 address space wastage on low-budget operating systems like OpenBSD

---
 vm/contexts.cpp | 11 +++++++++--
 vm/master.hpp   |  1 +
 vm/vm.hpp       |  2 +-
 3 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/vm/contexts.cpp b/vm/contexts.cpp
index 0ddd51e1be..3d3008c2ab 100644
--- a/vm/contexts.cpp
+++ b/vm/contexts.cpp
@@ -111,8 +111,8 @@ void factor_vm::init_contexts(cell datastack_size_, cell retainstack_size_, cell
 void factor_vm::delete_contexts()
 {
 	assert(!ctx);
-	std::vector<context *>::const_iterator iter = unused_contexts.begin();
-	std::vector<context *>::const_iterator end = unused_contexts.end();
+	std::list<context *>::const_iterator iter = unused_contexts.begin();
+	std::list<context *>::const_iterator end = unused_contexts.end();
 	while(iter != end)
 	{
 		delete *iter;
@@ -159,6 +159,13 @@ void factor_vm::delete_context(context *old_context)
 {
 	unused_contexts.push_back(old_context);
 	active_contexts.erase(old_context);
+
+	while(unused_contexts.size() > 10)
+	{
+		context *stale_context = unused_contexts.front();
+		unused_contexts.pop_front();
+		delete stale_context;
+	}
 }
 
 VM_C_API void delete_context(factor_vm *parent, context *old_context)
diff --git a/vm/master.hpp b/vm/master.hpp
index d2b9a5f709..d4cd70f867 100755
--- a/vm/master.hpp
+++ b/vm/master.hpp
@@ -24,6 +24,7 @@
 
 /* C++ headers */
 #include <algorithm>
+#include <list>
 #include <map>
 #include <set>
 #include <vector>
diff --git a/vm/vm.hpp b/vm/vm.hpp
index 2cbedbcc7b..d9c7186c4e 100755
--- a/vm/vm.hpp
+++ b/vm/vm.hpp
@@ -35,7 +35,7 @@ struct factor_vm
 	int callback_id;
 
 	/* Pooling unused contexts to make context allocation cheaper */
-	std::vector<context *> unused_contexts;
+	std::list<context *> unused_contexts;
 
 	/* Active contexts, for tracing by the GC */
 	std::set<context *> active_contexts;