[sgen] Try allocating M&S blocks in smaller contingents in case of failure.

This might happen when the address space fragments.  If it happens due to
OOM, we're probably lost anyway.

diff --git a/mono/metadata/sgen-marksweep.c b/mono/metadata/sgen-marksweep.c
index 29063e13d2a6132e9529d48ffa95be4704cbdd2a..c5504223eb23f899dfdb38f868919f05641bd1e4 100644 (file)
--- a/mono/metadata/sgen-marksweep.c
+++ b/mono/metadata/sgen-marksweep.c
@@ -363,9 +363,21 @@ ms_get_empty_block (void)
 
  retry:
        if (!empty_blocks) {
-               p = sgen_alloc_os_memory_aligned (MS_BLOCK_SIZE * MS_BLOCK_ALLOC_NUM, MS_BLOCK_SIZE, SGEN_ALLOC_HEAP | SGEN_ALLOC_ACTIVATE, "major heap section");
+               /*
+                * We try allocating MS_BLOCK_ALLOC_NUM blocks first.  If that's
+                * unsuccessful, we halve the number of blocks and try again, until we're at
+                * 1.  If that doesn't work, either, we assert.
+                */
+               int alloc_num = MS_BLOCK_ALLOC_NUM;
+               for (;;) {
+                       p = sgen_alloc_os_memory_aligned (MS_BLOCK_SIZE * alloc_num, MS_BLOCK_SIZE, SGEN_ALLOC_HEAP | SGEN_ALLOC_ACTIVATE,
+                                       alloc_num == 1 ? "major heap section" : NULL);
+                       if (p)
+                               break;
+                       alloc_num >>= 1;
+               }
 
-               for (i = 0; i < MS_BLOCK_ALLOC_NUM; ++i) {
+               for (i = 0; i < alloc_num; ++i) {
                        block = p;
                        /*
                         * We do the free list update one after the
@@ -379,9 +391,9 @@ ms_get_empty_block (void)
                        p += MS_BLOCK_SIZE;
                }
 
-               SGEN_ATOMIC_ADD (num_empty_blocks, MS_BLOCK_ALLOC_NUM);
+               SGEN_ATOMIC_ADD (num_empty_blocks, alloc_num);
 
-               stat_major_blocks_alloced += MS_BLOCK_ALLOC_NUM;
+               stat_major_blocks_alloced += alloc_num;
        }
 
        do {