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* Don't allocate a big initial GC address space on machines with

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little RAM.  Even if the memory isn't actually used, it can cause
  problems with the overcommit heuristics in the kernel.  So use a VM
  space of 25% of RAM, up to 384 MB.
This commit is contained in:
Eelco Dolstra 2011-02-10 14:31:04 +00:00
parent 5a6b039802
commit 538b7caab0
2 changed files with 25 additions and 12 deletions
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35
src/libexpr/eval.cc
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@ -7,6 +7,7 @@
#include "globals.hh"
#include <cstring>
#include <unistd.h>
#if HAVE_BOEHMGC
@ -155,17 +156,29 @@ EvalState::EvalState()
#if HAVE_BOEHMGC
static bool gcInitialised = true;
if (gcInitialised) {
/* 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.) 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(384 * 1024 * 1024);
/* Set the initial heap size to something fairly big (25% of
physical RAM, up to a maximum of 384 MiB) so that in most
cases we don't need to garbage collect at all. (Collection
has a fairly significant overhead.) 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")) {
size_t maxSize = 384 * 1024 * 1024;
size_t size = 32 * 1024 * 1024;
#if HAVE_SYSCONF && defined(_SC_PAGESIZE) && defined(_SC_PHYS_PAGES)
long pageSize = sysconf(_SC_PAGESIZE);
long pages = sysconf (_SC_PHYS_PAGES);
if (pageSize != -1 && size != -1)
size = (pageSize * pages) / 4; // 25% of RAM
if (size > maxSize) size = maxSize;
#endif
debug(format("setting initial heap size to %1% bytes") % size);
GC_expand_hp(size);
}
gcInitialised = true;
}
#endif