Question

我正在使用

运行示例程序程序

rahul@g3ck0:~/programs/Remodel$ GOGCTRACE=1 go run main.go 
gc1(1): 0+0+0 ms 0 -> 0 MB 422 -> 346 (422-76) objects 0 handoff
gc2(1): 0+0+0 ms 0 -> 0 MB 2791 -> 1664 (2867-1203) objects 0 handoff
gc3(1): 0+0+0 ms 1 -> 0 MB 4576 -> 2632 (5779-3147) objects 0 handoff
gc4(1): 0+0+0 ms 1 -> 0 MB 3380 -> 2771 (6527-3756) objects 0 handoff
gc5(1): 0+0+0 ms 1 -> 0 MB 3511 -> 2915 (7267-4352) objects 0 handoff
gc6(1): 0+0+0 ms 1 -> 0 MB 6573 -> 2792 (10925-8133) objects 0 handoff
gc7(1): 0+0+0 ms 1 -> 0 MB 4859 -> 3059 (12992-9933) objects 0 handoff
gc8(1): 0+0+0 ms 1 -> 0 MB 4554 -> 3358 (14487-11129) objects 0 handoff
gc9(1): 0+0+0 ms 1 -> 0 MB 8633 -> 4116 (19762-15646) objects 0 handoff
gc10(1): 0+0+0 ms 1 -> 0 MB 9415 -> 4769 (25061-20292) objects 0 handoff
gc11(1): 0+0+0 ms 1 -> 0 MB 6636 -> 4685 (26928-22243) objects 0 handoff
gc12(1): 0+0+0 ms 1 -> 0 MB 6741 -> 4802 (28984-24182) objects 0 handoff
gc13(1): 0+0+0 ms 1 -> 0 MB 9654 -> 5097 (33836-28739) objects 0 handoff
gc1(1): 0+0+0 ms 0 -> 0 MB 209 -> 171 (209-38) objects 0 handoff

帮助我理解第一部分，即

0 + 0 + 0 =＆gt;标记+扫描+清洁时间

422 - ＆gt; 346意味着内存清理从422MB到346 MB？如果是的话，那么当没有什么东西可以清理时，内存是如何减少的呢？

Answer 1

在Go 1.5中，此输出的格式发生了很大变化。有关完整文档，请转到http://godoc.org/runtime并搜索＆＃34; gctrace：＆＃34;

gctrace: setting gctrace=1 causes the garbage collector to emit a single line to standard
error at each collection, summarizing the amount of memory collected and the
length of the pause. Setting gctrace=2 emits the same summary but also
repeats each collection. The format of this line is subject to change.
Currently, it is:
    gc # @#s #%: #+...+# ms clock, #+...+# ms cpu, #->#-># MB, # MB goal, # P
where the fields are as follows:
    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
The phases are stop-the-world (STW) sweep termination, scan,
synchronize Ps, mark, and STW mark termination. The CPU times
for mark are broken down in to assist time (GC performed in
line with allocation), background GC time, and idle GC time.
If the line ends with "(forced)", this GC was forced by a
runtime.GC() call and all phases are STW.

Answer 2

输出是从此行生成的：http://golang.org/src/pkg/runtime/mgc0.c?#L2147

所以不同的部分是：

0 + 0 + 0 ms：以ms为单位标记，扫描和清除持续时间
1 - ＆gt; 0 MB：MB之前和之后的堆
209 - 171：
（209-38）个对象：分配和释放的数量

切换（以及Go 1.2窃取和收益）是算法的内部。

解密golang垃圾收集输出

2 个答案: