From d75cfe191c4e97bdacfe7aaa9415e47869f829ea Mon Sep 17 00:00:00 2001
From: Richard Brooksby <rb@ravenbrook.com>
Date: Tue, 28 Jan 2014 19:15:41 +0000
Subject: [PATCH] Incorporating early commit limit checking into arena
 allocation policy.

Copied from Perforce
 Change: 184240
 ServerID: perforce.ravenbrook.com
---
 mps/code/arena.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/mps/code/arena.c b/mps/code/arena.c
index 54755a2fc31..6f961164c8e 100644
--- a/mps/code/arena.c
+++ b/mps/code/arena.c
@@ -697,7 +697,7 @@ failMark:
  * can be maintained and adjusted.
  */
 
-static Res arenaAllocPolicy(Tract *tractReturn, SegPref pref,
+static Res arenaAllocPolicy(Tract *tractReturn, Arena arena, SegPref pref,
                             Size size, Pool pool)
 {
   Res res;
@@ -708,6 +708,16 @@ static Res arenaAllocPolicy(Tract *tractReturn, SegPref pref,
   AVER(size > (Size)0);
   AVERT(Pool, pool);
 
+  /* Don't attempt to allocate if doing so would definitely exceed the
+     commit limit. */
+  if (arena->spareCommitted < size) {
+    Size necessaryCommitIncrease = size - arena->spareCommitted;
+    if (arena->committed + necessaryCommitIncrease > arena->commitLimit
+        || arena->committed + necessaryCommitIncrease < arena->committed) {
+      return ResCOMMIT_LIMIT;
+    }
+  }
+
   /* Plan A: allocate from the free CBS in the requested zones */
   /* FIXME: Takes no account of other zones fields */
   res = arenaAllocFromCBS(&tract, pref->zones, size, pool);
@@ -754,7 +764,7 @@ Res ArenaAlloc(Addr *baseReturn, SegPref pref, Size size, Pool pool,
     }
   }
 
-  res = arenaAllocPolicy(&tract, pref, size, pool);
+  res = arenaAllocPolicy(&tract, arena, pref, size, pool);
   if (res != ResOK) {
     if (withReservoirPermit) {
       Res resRes = ReservoirWithdraw(&base, &tract, reservoir, size, pool);