From e11e6fb1c6709ca3f0e596a7b1fb988df2fbd9b1 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <e.dolstra@tudelft.nl>
Date: Thu, 28 Oct 2010 12:29:40 +0000
Subject: * Handle out of memory condition.

---
 src/libmain/shared.cc | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

(limited to 'src/libmain/shared.cc')

diff --git a/src/libmain/shared.cc b/src/libmain/shared.cc
index eddc4e64b3d7..440949bd2a0a 100644
--- a/src/libmain/shared.cc
+++ b/src/libmain/shared.cc
@@ -13,6 +13,10 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
+#if HAVE_BOEHMGC
+#include <gc/gc.h>
+#endif
+
 
 namespace nix {
 
@@ -314,6 +318,14 @@ static void setuidInit()
 }
 
 
+/* Called when the Boehm GC runs out of memory. */
+static void * oomHandler(size_t requested)
+{
+    /* Convert this to a proper C++ exception. */
+    throw std::bad_alloc();
+}
+
+
 }
 
 
@@ -335,6 +347,14 @@ int main(int argc, char * * argv)
 
     std::ios::sync_with_stdio(false);
 
+#if HAVE_BOEHMGC
+    /* Initialise the Boehm garbage collector.  This isn't necessary
+       on most platforms, but for portability we do it anyway. */
+    GC_INIT();
+
+    GC_oom_fn = oomHandler;
+#endif
+
     try {
         try {
             initAndRun(argc, argv);
-- 
cgit 1.4.1


From 14fbf85380b23efcc19c8479b65336fc7275d90b Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <e.dolstra@tudelft.nl>
Date: Fri, 29 Oct 2010 13:11:50 +0000
Subject: * Set libgc's initial heap size to 384 MiB to prevent garbage  
 collection in most cases (and therefore its performance overhead).

---
 src/libmain/shared.cc | 12 ++++++++++++
 1 file changed, 12 insertions(+)

(limited to 'src/libmain/shared.cc')

diff --git a/src/libmain/shared.cc b/src/libmain/shared.cc
index 440949bd2a0a..82309544a62d 100644
--- a/src/libmain/shared.cc
+++ b/src/libmain/shared.cc
@@ -353,6 +353,18 @@ int main(int argc, char * * argv)
     GC_INIT();
 
     GC_oom_fn = oomHandler;
+
+    /* Set the initial heap size to something fairly big (384 MiB) so
+       that in most cases we don't need to garbage collect at all.
+       (Collection has a fairly significant overhead, some.)  The heap
+       size can be overriden through libgc's GC_INITIAL_HEAP_SIZE
+       environment variable.  We should probably also provide a
+       nix.conf setting for this.  Note that GC_expand_hp() causes a
+       lot of virtual, but not physical (resident) memory to be
+       allocated.  This might be a problem on systems that don't
+       overcommit. */
+    if (!getenv("GC_INITIAL_HEAP_SIZE"))
+        GC_expand_hp(384000000);
 #endif
 
     try {
-- 
cgit 1.4.1


From 26def5392f6f6364aa0939a2d4fc7705e786d38d Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <e.dolstra@tudelft.nl>
Date: Fri, 29 Oct 2010 14:44:02 +0000
Subject: * Document Boehm GC support.

---
 doc/manual/env-common.xml    | 11 +++++++++++
 doc/manual/installation.xml  |  7 +++++++
 doc/manual/release-notes.xml | 21 +++++++++++++++++++++
 src/libmain/shared.cc        |  2 +-
 4 files changed, 40 insertions(+), 1 deletion(-)

(limited to 'src/libmain/shared.cc')

diff --git a/doc/manual/env-common.xml b/doc/manual/env-common.xml
index d67ef714d0f9..99acc5949044 100644
--- a/doc/manual/env-common.xml
+++ b/doc/manual/env-common.xml
@@ -271,6 +271,17 @@ $ mount -o bind /mnt/otherdisk/nix /nix</screen>
 
 </varlistentry>
 
+
+<varlistentry><term><envar>GC_INITIAL_HEAP_SIZE</envar></term>
+
+  <listitem><para>If Nix has been configured to use the Boehm garbage
+  collector, this variable sets the initial size of the heap in bytes.
+  It defaults to 384 MiB.  Setting it to a low value reduces memory
+  consumption, but will increase runtime due to the overhead of
+  garbage collection.</para></listitem>
+
+</varlistentry>
+
     
 </variablelist>
 
diff --git a/doc/manual/installation.xml b/doc/manual/installation.xml
index bc5e21f0d39a..87a6c446a2d5 100644
--- a/doc/manual/installation.xml
+++ b/doc/manual/installation.xml
@@ -105,6 +105,13 @@ this packages.  Alternatively, if you already have it installed, you
 can use <command>configure</command>'s <option>--with-bzip2</option>
 options to point to their respective locations.</para>
 
+<para>Nix can optionally use the <link
+xlink:href="http://www.hpl.hp.com/personal/Hans_Boehm/gc/">Boehm
+garbage collector</link> to reduce the evaluator’s memory consumption.
+To enable it, install <literal>pkgconfig</literal> and the Boehm
+garbage collector, and pass the flag <option>--enable-gc</option> to
+<command>configure</command>.</para>
+
 </section>
 
 
diff --git a/doc/manual/release-notes.xml b/doc/manual/release-notes.xml
index 5b1c30bf8292..1e579a37b017 100644
--- a/doc/manual/release-notes.xml
+++ b/doc/manual/release-notes.xml
@@ -6,6 +6,27 @@
 
 
 
+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-1.0"><title>Release 1.0 (TBA)</title>
+
+<para>This release has the following improvements:</para>
+
+<itemizedlist>
+
+  <listitem>
+    <para>Nix can now optionally use the Boehm garbage collector.
+    This significantly reduces the Nix evaluator’s memory footprint,
+    especially when evaluating large NixOS system configurations.  It
+    can be enabled using the <option>--enable-gc</option> configure
+    option.</para>
+  </listitem>
+
+</itemizedlist>
+
+</section>
+
+
 <!--==================================================================-->
 
 <section xml:id="ssec-relnotes-0.16"><title>Release 0.16 (August 17, 2010)</title>
diff --git a/src/libmain/shared.cc b/src/libmain/shared.cc
index 82309544a62d..29fc13e33627 100644
--- a/src/libmain/shared.cc
+++ b/src/libmain/shared.cc
@@ -364,7 +364,7 @@ int main(int argc, char * * argv)
        allocated.  This might be a problem on systems that don't
        overcommit. */
     if (!getenv("GC_INITIAL_HEAP_SIZE"))
-        GC_expand_hp(384000000);
+        GC_expand_hp(384 * 1024 * 1024);
 #endif
 
     try {
-- 
cgit 1.4.1