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runtime: Do not reserve huge amount of swap on 32 bit architectures.

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The mmap() call which reserves the arena should have MAP_NORESERVE
flag as in typical cases this memory will never be (fully) needed.
This matters in environments which do not do Linux style memory
overcommit, such as OpenIndiana/OpenSolaris/Solaris.

The MAP_NORESERVE flag does not exist on all operating systems
(for example FreeBSD). Therefore we define it to zero value in
case it does not exist.

Fixes issue 21.

From-SVN: r196088
This commit is contained in:
Ian Lance Taylor 2013-02-15 18:55:09 +00:00
parent 4dddfc74f3
commit 3ab98a471c
1 changed files with 9 additions and 1 deletions
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10
libgo/runtime/mem.c
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@ -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 @@ runtime_SysReserve(void *v, uintptr n)
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;