RFR: 8259404: Shenandoah: Fix time tracking in parallel_cleaning [v2]

[Aleksey Shipilev]

On Thu, 28 Jan 2021 19:09:49 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

>> Please review this patch fixes timing tracking for parallel cleaning.
>> 
>> Before:
>> `[9.844s][info][gc,stats] System Purge = 0.000 s (a = 76 us) (n = 1) (lvls, us = 76, 76, 76, 76, 76)` **<<== looks wrong**
>> `[9.844s][info][gc,stats] Unload Classes = 0.001 s (a = 541 us) (n = 1) (lvls, us = 541, 541, 541, 541, 541)`
>> `[9.844s][info][gc,stats] Weak Roots = 0.000 s (a = 75 us) (n = 1) (lvls, us = 75, 75, 75, 75, 75)`
>> `[9.844s][info][gc,stats] CLDG = 0.000 s (a = 0 us) (n = 1) (lvls, us = 0, 0, 0, 0, 0)`
>> After:
>> `[9.936s][info][gc,stats] System Purge = 0.001 s (a = 611 us) (n = 1) (lvls, us = 609, 609, 609, 609, 611)`
>> `[9.936s][info][gc,stats] Unload Classes = 0.000 s (a = 475 us) (n = 1) (lvls, us = 475, 475, 475, 475, 475)`
>> `[9.936s][info][gc,stats] DCU: <total> = 0.000 s (a = 162 us) (n = 1) (lvls, us = 160, 160, 160, 160, 162)`
>> `[9.936s][info][gc,stats] DCU: Code Cache Roots = 0.000 s (a = 162 us) (n = 1) (lvls, us = 160, 160, 160, 160, 162)`
>> `[9.936s][info][gc,stats] Weak Roots = 0.000 s (a = 105 us) (n = 1) (lvls, us = 105, 105, 105, 105, 105)`
>> `[9.936s][info][gc,stats] DWR: <total> = 0.000 s (a = 210 us) (n = 1) (lvls, us = 209, 209, 209, 209, 210)`
>> `[9.936s][info][gc,stats] DWR: VM Weak Roots = 0.000 s (a = 210 us) (n = 1) (lvls, us = 209, 209, 209, 209)`
>
> Zhengyu Gu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Aleksey's comments

Marked as reviewed by shade (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/2073