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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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2
configure.ac
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@ -284,7 +284,7 @@ AC_CHECK_FUNCS([setresuid setreuid lchown])
# Nice to have, but not essential. # Nice to have, but not essential.
AC_CHECK_FUNCS([strsignal posix_fallocate nanosleep]) AC_CHECK_FUNCS([strsignal posix_fallocate nanosleep sysconf])
# This is needed if ATerm or bzip2 are static libraries, # This is needed if ATerm or bzip2 are static libraries,

35
src/libexpr/eval.cc
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@ -7,6 +7,7 @@
#include "globals.hh" #include "globals.hh"
#include <cstring> #include <cstring>
#include <unistd.h>
#if HAVE_BOEHMGC #if HAVE_BOEHMGC
@ -155,17 +156,29 @@ EvalState::EvalState()
#if HAVE_BOEHMGC #if HAVE_BOEHMGC
static bool gcInitialised = true; static bool gcInitialised = true;
if (gcInitialised) { if (gcInitialised) {
/* Set the initial heap size to something fairly big (384 MiB) /* Set the initial heap size to something fairly big (25% of
so that in most cases we don't need to garbage collect at physical RAM, up to a maximum of 384 MiB) so that in most
all. (Collection has a fairly significant overhead.) The cases we don't need to garbage collect at all. (Collection
heap size can be overriden through libgc's has a fairly significant overhead.) The heap size can be
GC_INITIAL_HEAP_SIZE environment variable. We should overriden through libgc's GC_INITIAL_HEAP_SIZE environment
probably also provide a nix.conf setting for this. Note variable. We should probably also provide a nix.conf
that GC_expand_hp() causes a lot of virtual, but not setting for this. Note that GC_expand_hp() causes a lot of
physical (resident) memory to be allocated. This might be virtual, but not physical (resident) memory to be
a problem on systems that don't overcommit. */ allocated. This might be a problem on systems that don't
if (!getenv("GC_INITIAL_HEAP_SIZE")) overcommit. */
GC_expand_hp(384 * 1024 * 1024); 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; gcInitialised = true;
} }
#endif #endif