JDK-8281274: deal with ActiveProcessorCount in os::Linux::print_container_info #7354

MBaesken · 2022-02-04T16:18:38Z

The function os::Linux::print_container_info outputs memory- and cpu-related container information (when running in a containerized environment).
However in the case of active processor count , it currently just outputs the info from OSContainer::active_processor_count without looking at ActiveProcessorCount that can be set to overwrite the OSContainer::active_processor_count() - information. This should be improved.

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Issue

JDK-8281274: deal with ActiveProcessorCount in os::Linux::print_container_info

Reviewers

Thomas Stuefe (@tstuefe - Reviewer) ⚠️ Review applies to 2d84545
Severin Gehwolf (@jerboaa - Reviewer)
David Holmes (@dholmes-ora - Reviewer) ⚠️ Review applies to 2d84545
Ioi Lam (@iklam - Reviewer) ⚠️ Review applies to 2935242

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bridgekeeper · 2022-02-04T16:19:47Z

👋 Welcome back mbaesken! 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 · 2022-02-04T16:21:38Z

@MBaesken The following label will be automatically applied to this pull request:

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mlbridge · 2022-02-04T16:25:25Z

Webrevs

tstuefe

Looks fine.

While looking at this I found that the default for ActiveProcessorCount is -1. The VM only reacts to this flag if it is >0. So, what is 0? The java man page is not saying. Maybe the default should just be 0 to be consistent.

openjdk · 2022-02-04T17:28:07Z

@MBaesken This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8281274: deal with ActiveProcessorCount in os::Linux::print_container_info

Reviewed-by: stuefe, sgehwolf, dholmes, iklam

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 39 new commits pushed to the master branch:

f924e50: 8281440: AWT: Conversion from string literal loses const qualifier
072e7b4: 8272807: Permit use of memory concurrent with pretouch
cb2f8ca: 8281338: NSAccessibilityPressAction action for tree node and NSAccessibilityShowMenuAcgtion action not working
fc77217: 8281168: Micro-optimize VarForm.getMemberName for interpreter
bce5dd1: 8280438: Improve BufferNode::Allocator::release to avoid walking pending list
13f739d: 8280830: Change NonblockingQueue::try_pop variable named "result"
2f46af0: 8280132: Incorrect comparator com.sun.beans.introspect.MethodInfo.MethodOrder
fb17a8e: 8278947: Support for array constants in constant table
d658d94: 8280828: Improve invariants in NonblockingQueue::append
5fb56db: 8281476: ProblemList tools/jar/CreateMissingParentDirectories.java
... and 29 more: https://git.openjdk.java.net/jdk/compare/66b2c3b66e253ac3d8718c0c6d7c7551dbe04001...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

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

jerboaa · 2022-02-04T17:52:10Z

src/hotspot/os/linux/os_linux.cpp

@@ -2174,7 +2174,12 @@ bool os::Linux::print_container_info(outputStream* st) {
  int i = OSContainer::active_processor_count();
  st->print("active_processor_count: ");
  if (i > 0) {
-    st->print_cr("%d", i);
+    if (ActiveProcessorCount > 0) {
+      st->print_cr("%d, but overwritten by flag ActiveProcessorCount: %d",


This will print the same number (processor count) twice. I'd suggest to only add a blurb like " overridden by -XX:ActiveProcessorCount" in case the flag is set and not print the blurb otherwise.

Asserting the new output in the jtreg test would be good to have too.

This format is fine me with me. You want to see both the container processor count and the actual count being used.

Hi Severin , I adjusted the output following your suggestion (David, in case ActiveProcessorCount is set on the command line it is printed as well , see Arguments::print_summary_on , probably that's why Severin does not want it here.
Regarding , whether other info we present can be overridden by flags, I think not in the container area (not sure about the whole hs_err output).

Sorry, I was wrong. I misread int i = OSContainer::active_processor_count(); for int i = os::active_processor_count(); which would then return the same value. As @dholmes-ora said, the original format was fine. Please add this in the test, though. Could be akin to test/hotspot/jtreg/containers/docker/TestMisc.testPrintContainerInfo(). I.e. set some CPU quota and also ActiveProcessorCount and assert the message in log output.

Sorry, I was wrong. I misread int i = OSContainer::active_processor_count(); for int i = os::active_processor_count(); which would then return the same value. As @dholmes-ora said, the original format was fine. Please add this in the test, though. Could be akin to test/hotspot/jtreg/containers/docker/TestMisc.testPrintContainerInfo(). I.e. set some CPU quota and also ActiveProcessorCount and assert the message in log output.

Hi Severin, I adjusted the output again; also adjusted the jtreg test containers/docker/TestMisc .

Best regards, Matthias

jerboaa

Hmm, not sure why it recorded my comment as "approval".

dholmes-ora

Seems fine to me.

Does make me wonder whether other info we present can be overridden by flags.

Thanks,
David

dholmes-ora · 2022-02-04T22:05:39Z

src/hotspot/os/linux/os_linux.cpp

@@ -2174,7 +2174,12 @@ bool os::Linux::print_container_info(outputStream* st) {
  int i = OSContainer::active_processor_count();
  st->print("active_processor_count: ");
  if (i > 0) {
-    st->print_cr("%d", i);
+    if (ActiveProcessorCount > 0) {
+      st->print_cr("%d, but overwritten by flag ActiveProcessorCount: %d",


This format is fine me with me. You want to see both the container processor count and the actual count being used.

MBaesken · 2022-02-07T08:35:33Z

Looks fine.

While looking at this I found that the default for ActiveProcessorCount is -1. The VM only reacts to this flag if it is >0. So, what is 0? The java man page is not saying. Maybe the default should just be 0 to be consistent.

Thanks for the review. Indeed only ActiveProcessorCount > 0 results in special handling, so 0 and -1 are both leading to the same runtime behavior.

jerboaa · 2022-02-07T16:15:41Z

test/hotspot/jtreg/containers/docker/TestMisc.java

@@ -86,7 +86,7 @@ private static void testIsContainerized() throws Exception {
    private static void testPrintContainerInfo() throws Exception {
        Common.logNewTestCase("Test print_container_info()");

-        DockerRunOptions opts = Common.newOpts(imageName, "PrintContainerInfo");
+        DockerRunOptions opts = Common.newOpts(imageName, "PrintContainerInfo", "-XX:ActiveProcessorCount=2");


It would be better to separate this specific test. More like this:
jerboaa@3911ef8

I'm not sure I like this version of the test better. I'd rather separate concerns. The changes to Common aren't really needed, as Common.newOpts(imageName, "PrintContainerInfo").addJavaOpts("-XX:ActiveProcessorCount=2"); can be used instead. Similarly, the changes to checkContainerInfo() make the test harder to read. It's once called with a null argument and checks similar things, but one additional assert. Rather than that, I'd just do the assert directly in the new test as suggested. This saves the reader having to look up call-sites to know what the test is actually asserting. This also more closely matches what's likely to happen in real scenarios (override the container detection heuristics with -XX:ActiveProcessorCount).

dholmes-ora · 2022-02-08T02:40:02Z

test/lib/jdk/test/lib/containers/docker/Common.java

@@ -71,6 +71,14 @@ public static DockerRunOptions newOpts(String imageNameAndTag, String testClass)
        return opts;
    }

+    public static DockerRunOptions newOpts(String imageNameAndTag, String testClass, String addJavaOpts) {


It would be good to avoid code duplication and just e.g. have the no-arg newOpts pass null for addJavaOpts.

…uplication in Common

MBaesken · 2022-02-08T15:18:13Z

Hi David and Severin, I added a separate test to TestMisc. Additionally I adjusted Common.java to avoid code duplication.
Thanks, Matthias

jerboaa · 2022-02-08T17:30:14Z

test/hotspot/jtreg/containers/docker/TestMisc.java

@@ -86,7 +86,7 @@ private static void testIsContainerized() throws Exception {
    private static void testPrintContainerInfo() throws Exception {
        Common.logNewTestCase("Test print_container_info()");

-        DockerRunOptions opts = Common.newOpts(imageName, "PrintContainerInfo");
+        DockerRunOptions opts = Common.newOpts(imageName, "PrintContainerInfo", "-XX:ActiveProcessorCount=2");


I'm not sure I like this version of the test better. I'd rather separate concerns. The changes to Common aren't really needed, as Common.newOpts(imageName, "PrintContainerInfo").addJavaOpts("-XX:ActiveProcessorCount=2"); can be used instead. Similarly, the changes to checkContainerInfo() make the test harder to read. It's once called with a null argument and checks similar things, but one additional assert. Rather than that, I'd just do the assert directly in the new test as suggested. This saves the reader having to look up call-sites to know what the test is actually asserting. This also more closely matches what's likely to happen in real scenarios (override the container detection heuristics with -XX:ActiveProcessorCount).

iklam

LGTM

MBaesken · 2022-02-09T08:11:01Z

Hi Severin, indeed we can live without changing Common.java; adjusted the test.
Best regards, Matthias

MBaesken · 2022-02-09T11:31:32Z

/integrate

openjdk · 2022-02-09T11:33:29Z

Going to push as commit bb2e10c.
Since your change was applied there have been 41 commits pushed to the master branch:

69e390a: 8262721: Add Tests to verify single iteration loops are properly optimized
f092bab: 8281195: Mistakenly used logging causes significant overhead in interpreter
f924e50: 8281440: AWT: Conversion from string literal loses const qualifier
072e7b4: 8272807: Permit use of memory concurrent with pretouch
cb2f8ca: 8281338: NSAccessibilityPressAction action for tree node and NSAccessibilityShowMenuAcgtion action not working
fc77217: 8281168: Micro-optimize VarForm.getMemberName for interpreter
bce5dd1: 8280438: Improve BufferNode::Allocator::release to avoid walking pending list
13f739d: 8280830: Change NonblockingQueue::try_pop variable named "result"
2f46af0: 8280132: Incorrect comparator com.sun.beans.introspect.MethodInfo.MethodOrder
fb17a8e: 8278947: Support for array constants in constant table
... and 31 more: https://git.openjdk.java.net/jdk/compare/66b2c3b66e253ac3d8718c0c6d7c7551dbe04001...master

Your commit was automatically rebased without conflicts.

openjdk · 2022-02-09T11:33:52Z

@MBaesken Pushed as commit bb2e10c.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

dholmes-ora

Only a single reviewer approved the final version of these changes so it may have been prudent to seek a least one additional re-review. I had it on my to-do list. :)

The updated test looks much cleaner and simpler.

Thanks,
David

JDK-8281274

2d84545

openjdk bot added the rfr Pull request is ready for review label Feb 4, 2022

openjdk bot added the hotspot-runtime hotspot-runtime-dev@openjdk.org label Feb 4, 2022

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Adjust output

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Adjust output again, adjust test

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Add separate testPrintContainerInfoActiveProcessorCount, avoid code d…

2935242

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Avoid changing Common.java, simplify test

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JDK-8281274: deal with ActiveProcessorCount in os::Linux::print_container_info #7354

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JDK-8281274: deal with ActiveProcessorCount in os::Linux::print_container_info #7354

JDK-8281274: deal with ActiveProcessorCount in os::Linux::print_container_info #7354

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