chan: allocate a new chan with one

malloc rather than nelements + 1.

R=rob
CC=golang-dev
https://golang.org/cl/4291064

diff --git a/src/pkg/runtime/chan.c b/src/pkg/runtime/chan.c
index 2dee38b470ddec4cec3839d2076ecd0b800b58d8..551b07fe2a643bb021e06f3ec83be878a5a8b7e8 100644 (file)
--- a/src/pkg/runtime/chan.c
+++ b/src/pkg/runtime/chan.c
@@ -5,6 +5,8 @@
 #include "runtime.h"
 #include "type.h"
 
+#define        MAXALIGN        7
+
 static int32   debug   = 0;
 
 typedef        struct  Link    Link;
@@ -95,7 +97,9 @@ Hchan*
 runtime·makechan_c(Type *elem, int64 hint)
 {
        Hchan *c;
-       int32 i;
+       int32 i, m, n;
+       Link *d, *b, *e;
+       byte *by;
 
        if(hint < 0 || (int32)hint != hint || hint > ((uintptr)-1) / elem->size)
                runtime·panicstring("makechan: size out of range");
@@ -105,7 +109,19 @@ runtime·makechan_c(Type *elem, int64 hint)
                runtime·throw("runtime.makechan: unsupported elem type");
        }
 
-       c = runtime·mal(sizeof(*c));
+       // calculate rounded sizes of Hchan and Link
+       n = sizeof(*c);
+       while(n & MAXALIGN)
+               n++;
+       m = sizeof(*d) + elem->size - sizeof(d->elem);
+       while(m & MAXALIGN)
+               m++;
+
+       // allocate memory in one call
+       by = runtime·mal(n + hint*m);
+
+       c = (Hchan*)by;
+       by += n;
        runtime·addfinalizer(c, destroychan, 0);
 
        c->elemsize = elem->size;
@@ -113,13 +129,13 @@ runtime·makechan_c(Type *elem, int64 hint)
        c->elemalign = elem->align;
 
        if(hint > 0) {
-               Link *d, *b, *e;
 
                // make a circular q
                b = nil;
                e = nil;
                for(i=0; i<hint; i++) {
-                       d = runtime·mal(sizeof(*d) + c->elemsize - sizeof(d->elem));
+                       d = (Link*)by;
+                       by += m;
                        if(e == nil)
                                e = d;
                        d->link = b;