path: root/doc/README.environment
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Diffstat (limited to 'doc/README.environment')
1 files changed, 50 insertions, 2 deletions
diff --git a/doc/README.environment b/doc/README.environment
index 5760342..fcc81a5 100644
--- a/doc/README.environment
+++ b/doc/README.environment
@@ -1,5 +1,5 @@
The garbage collector looks at a number of environment variables which are
-the used to affect its operation. These are examined only on Un*x-like
+then used to affect its operation. These are examined only on Un*x-like
GC_INITIAL_HEAP_SIZE=<bytes> - Initial heap size in bytes. May speed up
@@ -27,11 +27,59 @@ GC_PRINT_ADDRESS_MAP - Linux only. Dump /proc/self/maps, i.e. various address
GC_NPROCS=<n> - Linux w/threads only. Explicitly sets the number of processors
that the GC should expect to use. Note that setting this to 1
when multiple processors are available will preserve
- correctness, but may lead to really horrible performance.
+ correctness, but may lead to really horrible performance,
+ since the lock implementation will immediately yield without
+ first spinning.
+GC_MARKERS=<n> - Linux w/threads and parallel marker only. Set the number
+ of marker threads. This is normaly set to the number of
+ processors. It is safer to adjust GC_MARKERS than GC_NPROCS,
+ since GC_MARKERS has no impact on the lock implementation.
GC_NO_BLACKLIST_WARNING - Prevents the collector from issuing
"Needed to allocate blacklisted block at ..." warnings.
+GC_IGNORE_GCJ_INFO - Ignore the type descriptors implicitly supplied by
+ GC_gcj_malloc and friends. This is useful for debugging
+ descriptor generation problems, and possibly for
+ temporarily working around such problems. It forces a
+ fully conservative scan of all heap objects except
+ those known to be pointerfree, and may thus have other
+ adverse effects.
+GC_PRINT_BACK_HEIGHT - Print max length of chain through unreachable objects
+ ending in a reachable one. If this number remains
+ bounded, then the program is "GC robust". This ensures
+ that a fixed number of misidentified pointers can only
+ result in a bounded space leak. This currently only
+ works if debugging allocation is used throughout.
+ It increases GC space and time requirements appreciably.
+ This feature is still somewhat experimental, and requires
+ that the collector have been built with MAKE_BACK_GRAPH
+ defined. For details, see Boehm, "Bounding Space Usage
+ of Conservative Garbage Collectors", POPL 2001, or
+ .
+GC_ENABLE_INCREMENTAL - Turn on incremental collection at startup. Note that,
+ depending on platform and collector configuration, this
+ may involve write protecting pieces of the heap to
+ track modifications. These pieces may include pointerfree
+ objects or not. Although this is intended to be
+ transparent, it may cause unintended system call failures.
+ Use with caution.
+GC_PAUSE_TIME_TARGET - Set the desired garbage collector pause time in msecs.
+ This only has an effect if incremental collection is
+ enabled. If a collection requires appreciably more time
+ than this, the client will be restarted, and the collector
+ will need to do additional work to compensate. The
+ special value "999999" indicates that pause time is
+ unlimited, and the incremental collector will behave
+ completely like a simple generational collector. If
+ the collector is configured for parallel marking, and
+ run on a multiprocessor, incremental collection should
+ only be used with unlimited pause time.
The following turn on runtime flags that are also program settable. Checked
only during initialization. We expect that they will usually be set through
other means, but this may help with debugging and testing: