From ef17ba047bcfe96f49967f05d3af0f78bca454a3 Mon Sep 17 00:00:00 2001
From: Richard Brooksby <rb@ravenbrook.com>
Date: Fri, 26 Feb 2016 18:58:34 +0000
Subject: [PATCH] Purge spare committed memory when growing the arena fails due
 to the commit limit.

Copied from Perforce
 Change: 189362
 ServerID: perforce.ravenbrook.com
---
 mps/code/policy.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/mps/code/policy.c b/mps/code/policy.c
index dbcb33e278f..f90c4c485f5 100644
--- a/mps/code/policy.c
+++ b/mps/code/policy.c
@@ -77,6 +77,14 @@ Res PolicyAlloc(Tract *tractReturn, Arena arena, LocusPref pref,
   /* Plan C: Extend the arena, then try A and B again. */
   if (moreZones != ZoneSetEMPTY) {
     res = arena->class->grow(arena, pref, size);
+    /* If we can't extent because we hit the commit limit, try purging
+       some spare committed memory and try again.*/
+    /* TODO: This would be a good time to *remap* VM instead of
+       returning it to the OS. */
+    if (res == ResCOMMIT_LIMIT) {
+      if (arena->class->purgeSpare(arena, size) >= size)
+        res = arena->class->grow(arena, pref, size);
+    }
     if (res != ResOK)
       return res;
     if (zones != ZoneSetEMPTY) {