8253030: ZGC: Change ZMarkCompleteTimeout unit to microseconds

[pliden]

The ZMarkCompleteTimeout is currently specified in milliseconds, and its value is 1 (i.e. as low as it can be). In preparation for using a lower time out value than 1ms we should change the ZMarkCompleteTimeout unit to be microseconds, instead of milliseconds.

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Progress

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Issue

• JDK-8253030: ZGC: Change ZMarkCompleteTimeout unit to microseconds

Reviewers

• Kim Barrett (@kimbarrett - Reviewer)
• Stefan Karlsson (@stefank - Reviewer)
• Erik Österlund (@fisk - Reviewer)

Download

$ git fetch https://git.openjdk.java.net/jdk pull/120/head:pull/120
$ git checkout pull/120

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[mlbridge]

Webrevs

• 00: Full (269e0f0)

[kimbarrett]

Change looks good. But I wonder, why choose microseconds as the units? That seems to be almost never used in HotSpot.

[openjdk]

@pliden This change now passes all automated pre-integration checks. In addition to the automated checks, the change must also fulfill all project specific requirements

After integration, the commit message will be:

8253030: ZGC: Change ZMarkCompleteTimeout unit to microseconds

Reviewed-by: kbarrett, stefank, eosterlund

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Since the source branch of this PR was last updated there have been 19 commits pushed to the master branch:

• f978f6f: 8252689: Classes are loaded from jrt:/java.base even when CDS is used
• c5e63b6: 8248186: Move CDS C++ vtable code to cppVtables.cpp
• 03a4df0: 8244778: Archive full module graph in CDS
• 998ce78: 8252543: [JVMCI] Libgraal can deadlock in blocking compilation mode
• b1b0f0b: 8253066: typo in Stream.mapMulti
• 306b166: 8253033: CheckUnhandledOops check fails in ThreadSnapshot::initialize…
• 5c0d985: 8253060: remove test/hotspot/jtreg/test_env.sh
• 9525186: 8253031: git jcheck complains about invalid tags in jdk repo after fix for JDK-8252844
• 7f27d0b: 8236142: DocTrees should provide getCharacters(EntityTree)
• e7a1b9b: 8252981: ObjectMonitor::object() cleanup changes extracted from JDK-8247281
• ... and 9 more: https://git.openjdk.java.net/jdk/compare/44a74dac957ca7cc10eaddafb6bd32b74a8d84c8...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid automatic rebasing, please merge master into your branch, and then specify the current head hash when integrating, like this: /integrate f978f6fe8ab57ab815f61dc0571df955db2663d5.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[pliden]

@kimbarrett Thanks for reviewing. I used micros because it seems like the natural unit to use here. Using nanos seems a bit overkill, as we will never need that precision and it would just add a bunch of zeros to the constant, which I'm not sure would help readability. What unit did you have in mind?

[fisk]

Looks good.

[mlbridge]

Mailing list message from Kim Barrett on hotspot-gc-dev:

On Sep 11, 2020, at 5:52 AM, Per Lid?n <pliden at openjdk.java.net> wrote:

On Fri, 11 Sep 2020 01:16:34 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

The ZMarkCompleteTimeout is currently specified in milliseconds, and its value is 1 (i.e. as low as it can be). In
preparation for using a lower time out value than 1ms we should change the ZMarkCompleteTimeout unit to be
microseconds, instead of milliseconds.

Change looks good. But I wonder, why choose microseconds as the units? That seems to be almost never used in HotSpot.

@kimbarrett Thanks for reviewing. I used micros because it seems like the natural unit to use here. Using nanos seems a
bit overkill, as we will never need that precision and it would just add a bunch of zeros to the constant, which I'm
not sure would help readability. What unit did you have in mind?

Nanos would have been my choice, since that's widely used. The configuration
isn't user-facing, so some extra zeros doesn't seem important to me. But I
don't feel strongly about it; it just seemed an odd choice to me, since micros are
so rarely used elsewhere in our code.

I?ll go click the reviewed button now.

[pliden]

/integrate

[openjdk]

@pliden Since your change was applied there have been 19 commits pushed to the master branch:

• f978f6f: 8252689: Classes are loaded from jrt:/java.base even when CDS is used
• c5e63b6: 8248186: Move CDS C++ vtable code to cppVtables.cpp
• 03a4df0: 8244778: Archive full module graph in CDS
• 998ce78: 8252543: [JVMCI] Libgraal can deadlock in blocking compilation mode
• b1b0f0b: 8253066: typo in Stream.mapMulti
• 306b166: 8253033: CheckUnhandledOops check fails in ThreadSnapshot::initialize…
• 5c0d985: 8253060: remove test/hotspot/jtreg/test_env.sh
• 9525186: 8253031: git jcheck complains about invalid tags in jdk repo after fix for JDK-8252844
• 7f27d0b: 8236142: DocTrees should provide getCharacters(EntityTree)
• e7a1b9b: 8252981: ObjectMonitor::object() cleanup changes extracted from JDK-8247281
• ... and 9 more: https://git.openjdk.java.net/jdk/compare/44a74dac957ca7cc10eaddafb6bd32b74a8d84c8...master

Your commit was automatically rebased without conflicts.

Pushed as commit 07da3a1.

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