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libgo patch committed: Use MAP_NORESERVE
- From: Ian Lance Taylor <iant at google dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Fri, 15 Feb 2013 10:55:13 -0800
- Subject: libgo patch committed: Use MAP_NORESERVE
This patch from Janne Snabb changes libgo to use MAP_NORESERVE when
allocating the large memory arena. This makes no difference on
GNU/Linux but reportedly helps on OpenIndiana and OpenSolaris.
Bootstrapped and ran Go testsuite on x86_64-unknown-linux-gnu.
Committed to mainline.
Ian
diff -r 38275c614957 libgo/runtime/mem.c
--- a/libgo/runtime/mem.c Fri Feb 15 10:48:31 2013 -0800
+++ b/libgo/runtime/mem.c Fri Feb 15 10:49:37 2013 -0800
@@ -18,6 +18,10 @@
#endif
#endif
+#ifndef MAP_NORESERVE
+#define MAP_NORESERVE 0
+#endif
+
#ifdef USE_DEV_ZERO
static int dev_zero = -1;
#endif
@@ -134,7 +138,11 @@
return v;
}
- p = runtime_mmap(v, n, PROT_NONE, MAP_ANON|MAP_PRIVATE, fd, 0);
+ // Use the MAP_NORESERVE mmap() flag here because typically most of
+ // this reservation will never be used. It does not make sense
+ // reserve a huge amount of unneeded swap space. This is important on
+ // systems which do not overcommit memory by default.
+ p = runtime_mmap(v, n, PROT_NONE, MAP_ANON|MAP_PRIVATE|MAP_NORESERVE, fd, 0);
if(p == MAP_FAILED)
return nil;
return p;