From: Andi Kleen <a...@linux.intel.com>
Add a threshold to avoid freeing pages back too early to the OS.
This avoid virtual memory map fragmentation.
Based on a idea from Honza
ggc/doc/:
2011-10-08 Andi Kleen <a...@linux.intel.com>
PR other/50636
* invoke.texi (ggc-free-threshold, ggc-free-min): Add.
ggc/:
2011-10-08 Andi Kleen <a...@linux.intel.com>
PR other/50636
* ggc-page.c (ggc_collect): Add free threshold.
* params.def (GGC_FREE_THRESHOLD, GGC_FREE_MIN): Add.
---
gcc/doc/invoke.texi | 11 +++++++++++
gcc/ggc-page.c | 13 +++++++++----
gcc/params.def | 10 ++++++++++
3 files changed, 30 insertions(+), 4 deletions(-)
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index ef7ac68..6557f66 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -8837,6 +8837,17 @@ very large effectively disables garbage collection.
Setting this
parameter and @option{ggc-min-expand} to zero causes a full collection
to occur at every opportunity.
+@item ggc-free-threshold
+
+Only free memory back to the system when it would free more than this
+many percent of the total allocated memory. Default is 20 percent.
+This avoids memory fragmentation.
+
+@item ggc-free-min
+
+Only free memory back to the system when it would free more than this.
+Unit is kilobytes.
+
@item max-reload-search-insns
The maximum number of instruction reload should look backward for equivalent
register. Increasing values mean more aggressive optimization, making the
diff --git a/gcc/ggc-page.c b/gcc/ggc-page.c
index 6e08cda..cd1c41a 100644
--- a/gcc/ggc-page.c
+++ b/gcc/ggc-page.c
@@ -1968,14 +1968,19 @@ ggc_collect (void)
if (GGC_DEBUG_LEVEL >= 2)
fprintf (G.debug_file, "BEGIN COLLECTING\n");
+ /* Release the pages we freed the last time we collected, but didn't
+ reuse in the interim. But only do this if this would free a
+ reasonable number of pages. Otherwise hold on to them
+ to avoid virtual memory fragmentation. */
+ if (G.bytes_mapped - G.allocated >=
+ (PARAM_VALUE (GGC_FREE_THRESHOLD) / 100.0) * G.bytes_mapped &&
+ G.bytes_mapped - G.allocated >= (size_t)PARAM_VALUE (GGC_FREE_MIN) *
1024)
+ release_pages ();
+
/* Zero the total allocated bytes. This will be recalculated in the
sweep phase. */
G.allocated = 0;
- /* Release the pages we freed the last time we collected, but didn't
- reuse in the interim. */
- release_pages ();
-
/* Indicate that we've seen collections at this context depth. */
G.context_depth_collections = ((unsigned long)1 << (G.context_depth + 1)) -
1;
diff --git a/gcc/params.def b/gcc/params.def
index 5e49c48..ca28715 100644
--- a/gcc/params.def
+++ b/gcc/params.def
@@ -561,6 +561,16 @@ DEFPARAM(GGC_MIN_HEAPSIZE,
#undef GGC_MIN_EXPAND_DEFAULT
#undef GGC_MIN_HEAPSIZE_DEFAULT
+DEFPARAM(GGC_FREE_THRESHOLD,
+ "ggc-free-threshold",
+ "Dont free memory back to system less this percent of the total memory",
+ 20, 0, 100)
+
+DEFPARAM(GGC_FREE_MIN,
+ "ggc-free-min",
+ "Dont free less memory than this back to the system, in kilobytes",
+ 8 * 1024, 0, 0)
+
DEFPARAM(PARAM_MAX_RELOAD_SEARCH_INSNS,
"max-reload-search-insns",
"The maximum number of instructions to search backward when looking
for equivalent reload",
--
1.7.5.4
