results

$ for t in build get main; do python parse.py $t.trace; done

# a trace of "go build file"
Malloc trace of 75809 mallocs over 5 cores
	Cache line shared 2266 (2.99%) times
	Cache line cold missed 12022 (15.86%) times

# a trace of "go get package"
Malloc trace of 163991 mallocs over 4 cores
	Cache line shared 7507 (4.58%) times
	Cache line cold missed 26232 (16.00%) times

# a trace of go.uik binary
Malloc trace of 25694 mallocs over 12 cores
	Cache line shared 3784 (14.73%) times
	Cache line cold missed 5219 (20.31%) times

parse.py

import fileinput
import re
import sys

total_mallocs = 0
cold_misses = 0
false_shares = 0

cache_line_size = 64
cache = {}

core_map = {}

def update(core, ptr):
	global total_mallocs
	global cold_misses
	global false_shares
	line = ptr / cache_line_size
	if line not in cache:
		cold_misses += 1
	elif cache[line] != core:
		false_shares += 1

	total_mallocs += 1

	core_map[core] = core
	cache[line] = core

regex = re.compile(r'([^ ]*) ([^ ]*)] malloc ([^ ]*) -> ([^ ]*)\n')
for line in fileinput.input(sys.argv[1:]):
	m = regex.match(line)
	if m is not None:
		g = m.groups()
		update(int(g[1]), int(g[3],16))

print "Malloc trace of %d mallocs over %d cores" % (total_mallocs, len(core_map))
print "\tCache line shared %d (%.2f%%) times" % (false_shares,
					       float(false_shares) /
					       float(total_mallocs) * 100)
print "\tCache line cold missed %d (%.2f%%) times" % (cold_misses,
					       float(cold_misses) /
					       float(total_mallocs) * 100)

runtime.diff

$ hg diff
diff -r 9a55b03991e3 src/pkg/runtime/malloc.goc
--- a/src/pkg/runtime/malloc.goc	Mon Apr 09 15:39:59 2012 -0400
+++ b/src/pkg/runtime/malloc.goc	Thu May 10 22:41:03 2012 -0400
@@ -93,6 +93,7 @@
 		}
 	}
 
+	runtime·printf("%D %d] malloc %d -> %p\n", runtime·nanotime(), m->id, size, v);
 	if(dogc && mstats.heap_alloc >= mstats.next_gc)
 		runtime·gc(0);
 	return v;