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;
