环境
本文的go版本是 go1.8 linux/amd64。
启动程序
设置环境变量GODEBUG，然后启动程序。假如程序叫proc，则启动命令为：
GODEBUG=gctrace=1 ./proc
gc信息
gc打印的内容像这样的：
gc 1 @0.045s 22%: 4.6+182+0.38 ms clock, 9.2+0/96/86+0.77 ms cpu, 52->52->52 MB, 53 MB goal, 2 P
gc打印的信息格式大概如下：
gc # @#s #%: #+...+# ms clock, #+...+# ms cpu, #->#-># MB, # MB goal, # P
字段含义如下:
gc # the GC number, incremented at each GC
@#s time in seconds since program start
#% percentage of time spent in GC since program start
#+...+# wall-clock/CPU times for the phases of the GC
#->#-># MB heap size at GC start, at GC end, and live heap
# MB goal goal heap size
# P number of processors used
参考：
http://stackoverflow.com/questions/20551748/decipher-golang-garbage-collection-output
