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On 5/21/19 6:25 AM, Thomas Stüfe wrote:
Hi Thomas,
On 2019-05-21 12:37, Thomas Stüfe wrote:
> I think this is useful.
Thanks.
I have a vague preference for reusing VM.flags
> though - giving it the option to only print one flag -
instead of adding
> a new command.
So, we would have three different modes for VM.flags:
$ jcmd HelloSleep VM.flags
371:
-XX:CICompilerCount=15 -XX:ConcGCThreads=6
-XX:G1ConcRefinementThreads=23 -XX:G1HeapRegionSize=4194304
-XX:GCDrainStackTargetSize=64 -XX:InitialHeapSize=2113929216
-XX:MarkStackSize=4194304 -XX:MaxHeapSize=32178700288
-XX:MaxNewSize=19306381312 -XX:MinHeapDeltaBytes=4194304
-XX:NonNMethodCodeHeapSize=8182140
-XX:NonProfiledCodeHeapSize=121738050
-XX:ProfiledCodeHeapSize=121738050
-XX:ReservedCodeCacheSize=251658240
-XX:+SegmentedCodeCache -XX:+UseCompressedClassPointers
-XX:+UseCompressedOops -XX:+UseFastUnorderedTimeStamps
-XX:+UseG1GC
$ /localhome/java/jdk9/bin/jcmd HelloSleep VM.flags -all
371:
[Global flags]
ccstrlist AOTLibrary =
{product} {default}
int ActiveProcessorCount = -1
{product} {default}
uintx AdaptiveSizeDecrementScaleFactor = 4
{product} {default}
uintx AdaptiveSizeMajorGCDecayTimeScale = 10
{product} {default}
uintx AdaptiveSizePolicyCollectionCostMargin = 50
{product} {default}
and a new mode:
$ /localhome/java/jdk9/bin/jcmd HelloSleep VM.flags
-name=UseSerialGC
371:
bool UseSerialGC = false
{product} {default}
Let's see if anyone else has some feedback regarding this.
Thanks,
StefanK
As I write, slight preference only. If others like
VM.get_flag more, I am fine with that too, since it
complements the existing VM.set_flag.
Given we have set_flag, I think get_flag makes more sense.
Chris
..Thomas
>
> Just my 5c
>
> .. Thomas
>
> On Tue, May 21, 2019, 12:14 Stefan Karlsson <stefan.karls...@oracle.com
> <mailto:stefan.karls...@oracle.com>>
wrote:
>
> Hi all,
>
> Please review this patch to introduce a new
diagnostic command:
> VM.get_flag.
>
> http://cr.openjdk.java.net/~stefank/8224479/webrev.01/
> https://bugs.openjdk.java.net/browse/JDK-8224479
>
> Today we have:
>
> - VM.set_flag - which allows the user to set a
manageable flag
> - VM.flags - which allows the user to print all set
flags or print
> similar output as -XX:+PrintFlagsFinal
>
> I propose that we add a new command to print the
value of one flag.
>
> Output from help:
> ==========
> $ jcmd HelloSleep help VM.get_flag
> 1060:
> VM.get_flag
> Prints the value of a VM flag option.
>
> Impact: Low
>
> Permission:
java.lang.management.ManagementPermission(monitor)
>
> Syntax : VM.get_flag <flag name>
>
> Arguments:
> flag name : The name of the flag we want
to get (STRING,
> no default value)
> ==========
>
> Output from usage:
> ==========
> $ jcmd HelloSleep VM.get_flag UseSerialGC
> 1060:
> false
> ==========
>
> I'll create a CSR if others also thinks this is a
worthwhile feature.
>
> Thanks,
> StefanK
>
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