慾海golang垃圾收集輸出

Question

我當時正在使用

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 

幫助我理解了第一部分，即

0 + 0 + 0 =>標記+掃描+清潔倍

樣本程序的程序

是否422 - > 346表示內存已經從422MB清理到346 MB？ 如果是的話，那麼當沒有什麼東西需要清理時，內存是如何減少的？

Answer 1

從該線產生的輸出：http://golang.org/src/pkg/runtime/mgc0.c?#L2147

所以不同部分是：

• 0 + 0 + 0 MS：標記，掃描和清潔的持續時間以毫秒
• 1 - > 0 MB：堆之前和之後在MB
• 209 - 171：對象之前和之後
• （209-38）對象：數allocs的並釋放

越區切換（以及在Go 1.2中的偷竊和收益）是算法的內部結構。

Answer 2

在Go 1.5中，此輸出的格式發生了很大變化。有關完整文檔，請轉至http://godoc.org/runtime並搜索「gctrace：」

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.