8371381: [Shenandoah] Setting ergo flags should use FLAG_SET_ERGO

[rgithubli]

Setting ergo flags using FLAG_SET_ERGO, instead of FLAG_SET_DEFAULT, so we can have the right origin info.

Had to expand ShenandoahEvacReserve range from range(1,100) to range(0,100) because when we use shenandoah passive mode and degen is also turned off (-XX:ShenandoahGCMode=passive -XX:-ShenandoahDegeneratedGC), we set the ShenandoahEvacReserve to 0:

jdk/src/hotspot/share/gc/shenandoah/mode/shenandoahPassiveMode.cpp

Line 41 in c6a8027

SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahEvacReserve, 0);

The issue is surfaced now because FLAG_SET_DEFAULT doesn't check the range but FLAG_SET_ERGO does.

Testing: jtreg gc. GHA pending.

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change must be properly reviewed (2 reviews required, with at least 1 Reviewer, 1 Author)

Issue

• JDK-8371381: [Shenandoah] Setting ergo flags should use FLAG_SET_ERGO (Bug - P4)

Reviewers

• Y. Srinivas Ramakrishna (@ysramakrishna - Reviewer) 🔄 Re-review required (review applies to 1a5a09bf)
• Cesar Soares Lucas (@JohnTortugo - Committer) 🔄 Re-review required (review applies to 1a5a09bf)
• Xiaolong Peng (@pengxiaolong - Committer) 🔄 Re-review required (review applies to 1a5a09bf)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/28242/head:pull/28242
$ git checkout pull/28242

Update a local copy of the PR:
$ git checkout pull/28242
$ git pull https://git.openjdk.org/jdk.git pull/28242/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 28242

View PR using the GUI difftool:
$ git pr show -t 28242

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/28242.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back rgithubli! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

@rgithubli This change is no longer ready for integration - check the PR body for details.

[openjdk]

@rgithubli The following labels will be automatically applied to this pull request:

• hotspot-gc
• shenandoah

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing lists. If you would like to change these labels, use the /label pull request command.

[mlbridge]

Webrevs

• 01: Full - Incremental (65fc9878)
• 00: Full (1a5a09bf)

[ysramakrishna]

Reviewed the ergo flg setting macro changes. They look good to me.

For the passive mode that requires allowing evac reserve of 0, I'll request @kdnilsen or @earthling-amzn to review.

/reviewers 2

[openjdk]

@ysramakrishna
The total number of required reviews for this PR (including the jcheck configuration and the last /reviewers command) is now set to 2 (with at least 1 Reviewer, 1 Author).

[earthling-amzn]

Hmm, setting ShenandoahEvacReserve to zero will cause a divide by zero error in other modes (it will even cause a divide by zero error in the passive mode if ShenandoahDegeneratedGC is enabled). I'd rather contain the accommodation for this configuration to the passive mode, than accept values that will cause crashes. Could we "inline" the macro on line 41 and allow zero only for this special configuration (passive mode and only full gcs) by changing the "inlined" macro to use SET_DEFAULT still?

[earthling-amzn]

If we allow this, somebody will file a bug because -XX:ShenandoahEvacReserve=0 will cause other modes to crash with divide by zero error.

[rgithubli]

OK, I'll keep the range as it is (1,100), but instead of setting the default with ergo at here:

jdk/src/hotspot/share/gc/shenandoah/mode/shenandoahPassiveMode.cpp

Lines 40 to 42 in c6a8027

	if (!ShenandoahDegeneratedGC) {
	SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahEvacReserve, 0);
	}

I'll just use FLAG_SET_DEFAULT to bypass the check? We wouldn't have the data source origin in passive mode which is only meant to be diagnostic, but that's better than causing problems in the regular mode.

[rgithubli]

Ah, missed your general comment above. I think we're talking about the same solution. I'll update the passive mode to use FLAG_SET_DEFAULT.

[earthling-amzn]

Yeah, that's what I was suggesting. Thanks!