runtime: try extending arena size in 32-bit allocator.

If it didn't reach the limit, we can try extending the arena
before resorting to random memory mappings and praying for the
kernel to be kind.

Fixes #3173.

R=rsc, rsc
CC=golang-dev
https://golang.org/cl/5725045

diff --git a/src/pkg/runtime/malloc.goc b/src/pkg/runtime/malloc.goc
index af03f8018d2b72ff42b44b054070c3b8a33511cc..fbdd6bb021ff2e9e1afa01f5c550ca2da424177a 100644 (file)
--- a/src/pkg/runtime/malloc.goc
+++ b/src/pkg/runtime/malloc.goc
@@ -371,6 +371,22 @@ runtime·MHeap_SysAlloc(MHeap *h, uintptr n)
 {
        byte *p;
 
+       if(n > h->arena_end - h->arena_used) {
+               // We are in 32-bit mode, maybe we didn't use all possible address space yet.
+               // Reserve some more space.
+               byte *new_end;
+               uintptr needed;
+
+               needed = (uintptr)h->arena_used + n - (uintptr)h->arena_end;
+               // Round wanted arena size to a multiple of 256MB.
+               needed = (needed + (256<<20) - 1) & ~((256<<20)-1);
+               new_end = h->arena_end + needed;
+               if(new_end <= h->arena_start + MaxArena32) {
+                       p = runtime·SysReserve(h->arena_end, new_end - h->arena_end);
+                       if(p == h->arena_end)
+                               h->arena_end = new_end;
+               }
+       }
        if(n <= h->arena_end - h->arena_used) {
                // Keep taking from our reservation.
                p = h->arena_used;
@@ -392,7 +408,8 @@ runtime·MHeap_SysAlloc(MHeap *h, uintptr n)
                return nil;
 
        if(p < h->arena_start || p+n - h->arena_start >= MaxArena32) {
-               runtime·printf("runtime: memory allocated by OS not in usable range\n");
+               runtime·printf("runtime: memory allocated by OS (%p) not in usable range [%p,%p)\n",
+                       p, h->arena_start, h->arena_start+MaxArena32);
                runtime·SysFree(p, n);
                return nil;
        }