code review 6223050: runtime: faster GC mark phase

src/pkg/runtime/mgc0.c

 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 // Garbage collector.
 
 #include "runtime.h"
 #include "arch_GOARCH.h"
 #include "malloc.h"
 #include "stack.h"
@@ skipping 588 matching lines @@
         byte *p;
 
         work.nroot = 0;
 
         // mark data+bss.
         for(p=data; p<ebss; p+=DataBlock)
                 addroot(p, p+DataBlock < ebss ? DataBlock : ebss-p);
 
         for(gp=runtime·allg; gp!=nil; gp=gp->alllink) {
                 switch(gp->status){
-                        default:
-                                runtime·printf("unexpected G.status %d\n", gp->status);
-                                runtime·throw("mark - bad status");
-                        case Gdead:
-                                break;
-                        case Grunning:
-                                if(gp != g)
-                                        runtime·throw("mark - world not stopped");
-                                addstackroots(gp);
-                                break;
-                        case Grunnable:
-                        case Gsyscall:
-                        case Gwaiting:
-                                addstackroots(gp);
-                                break;
+                default:
+                        runtime·printf("unexpected G.status %d\n", gp->status);
+                        runtime·throw("mark - bad status");
+                case Gdead:
+                        break;
+                case Grunning:
+                        if(gp != g)
+                                runtime·throw("mark - world not stopped");
+                        addstackroots(gp);
+                        break;
+                case Grunnable:
+                case Gsyscall:
+                case Gwaiting:
+                        addstackroots(gp);
+                        break;
                 }
         }
 
         runtime·walkfintab(addfinroots);
 
         for(fb=allfin; fb; fb=fb->alllink)
                 addroot((byte*)fb->fin, fb->cnt*sizeof(fb->fin[0]));
 }
 
 static bool
@@ skipping 616 matching lines @@
         uintptr n;
 
         n = (h->arena_used - h->arena_start) / wordsPerBitmapWord;
         n = (n+bitmapChunk-1) & ~(bitmapChunk-1);
         if(h->bitmap_mapped >= n)
                 return;
 
         runtime·SysMap(h->arena_start - n, n - h->bitmap_mapped);
         h->bitmap_mapped = n;
 }