-XX:MetaspaceSize is correct? (original) (raw)

Yasumasa Suenaga yasuenag at gmail.com
Tue Apr 15 13:38:17 UTC 2014

I uploaded new webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8039867/webrev.01/

Please review and sponsoring.

Yasumasa

On 04/15/2014 12:48 PM, Yasumasa Suenaga wrote:

Jon,

I agree with you. MetaspaceSize is used as minimum value when JVM shrink capacity in MetaspaceGC::computenewsize() . So I will change description to "minimum" and upload new webrev.

Yasumasa 2014-04-15 7:58 GMT+09:00, Jon Masamitsu <jon.masamitsu at oracle.com>: Yasumasa,

It's hard to describe what this parameter is in a single sentence. "high-water-mark" doesn't mean much unless you know about how it is used in the GC. Although "initial" is not right in the description, "minimum" might be closer to a good description. I'm really not sure. Jon On 04/10/2014 05:20 AM, Yasumasa Suenaga wrote: I uploaded webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8039867/webrev.00/

Please review and sponsoring!

Yasumasa On 04/10/2014 12:37 PM, Yasumasa Suenaga wrote: Hi Jon, Thank you for replying. I filed this issue as JDK-8039867: Incorrect description: -XX:MetaspaceSize . I attached a patch to this entry. I will upload webrev later.

Thanks, Yasumasa

2014-04-10 6:51 GMT+09:00, Jon Masamitsu <jon.masamitsu at oracle.com>: On 04/09/2014 06:22 AM, Yasumasa Suenaga wrote: Hi all, I checked initial metaspace size through jcmd PerfCounter.print . However, it seems to be incorrect: - Java command: java -XX:-UseCompressedClassPointers -XX:+PrintFlagsFinal LongSleep - Output from -XX:+PrintFlagsFinal: uintx MetaspaceSize = 21807104 {pd product} - Result of "PerfCounter.print" sun.gc.metaspace.capacity=4194304 sun.gc.metaspace.maxCapacity=8388608 sun.gc.metaspace.minCapacity=0

I checked metaspace.cpp, initial size of metaspace is detected by InitialBootClassLoaderMetaspaceSize. However, description of MetaspaceSize in globals.hpp is "Initial size of Metaspaces (in bytes)" . Is description of MetaspaceSize is correct? Description is not correct. And this behavior is correct? Behavior is correct. I have two plan for this mismatch: A) Change description of MetaspaceSize MetaspaceSize is used to HWM in metaspace.cpp . So we should change description for this behavior. ------------ diff -r 48ce2e6e1add src/share/vm/runtime/globals.hpp --- a/src/share/vm/runtime/globals.hpp Fri Apr 04 10:04:44 2014 -0700 +++ b/src/share/vm/runtime/globals.hpp Wed Apr 09 22:05:18 2014 +0900 @@ -3160,7 +3156,7 @@ "non-daemon thread (in _bytes)") _ __ productpd(uintx, _MetaspaceSize, _ - "Initial size of Metaspaces (in _bytes)") _ + "Initial HWM of Metaspaces (in _bytes)") _ Explain what HWM is if you're going to use it. __ product(uintx, MaxMetaspaceSize, _maxuintx, _ "Maximum size of Metaspaces (in _bytes)") _ ------------ B) Remove InitialBootClassLoaderMetaspaceSize and use MetaspaceSize In currently, InitialBootClassLoaderMetaspaceSize is used to initialize metaspace. InitialBootClassLoaderMetaspaceSize is only to use for it. Thus we should remove this option and use MetaspaceSize to initialize metaspace. InitialBootClassLoaderMetaspaceSize is an optimization. It allows approximately enough space for the system classes without repeated allocations of Metaspaces. Not everyone agrees with this optimization but I would like it kept. ------------ diff -r 48ce2e6e1add src/share/vm/memory/metaspace.cpp --- a/src/share/vm/memory/metaspace.cpp Fri Apr 04 10:04:44 2014 -0700 +++ b/src/share/vm/memory/metaspace.cpp Wed Apr 09 22:05:18 2014 +0900 @@ -3172,7 +3172,7 @@ #endif // Initialize these before initializing the VirtualSpaceList - firstchunkwordsize = InitialBootClassLoaderMetaspaceSize / BytesPerWord; + firstchunkwordsize = MetaspaceSize / BytesPerWord; firstchunkwordsize = alignwordsizeup(firstchunkwordsize); // Make the first class chunk bigger than a medium chunk so it's not put // on the medium chunk list. The next chunk will be small and progress diff -r 48ce2e6e1add src/share/vm/runtime/globals.hpp --- a/src/share/vm/runtime/globals.hpp Fri Apr 04 10:04:44 2014 -0700 +++ b/src/share/vm/runtime/globals.hpp Wed Apr 09 22:05:18 2014 +0900 @@ -2333,10 +2333,6 @@ develop(bool, TraceClassLoaderData, _false, _ "Trace class loader loaderdata _lifetime") _ __ - product(uintx, _InitialBootClassLoaderMetaspaceSize, _ - NOTLP64(2200*K) _LP64ONLY(4*M), _ - "Initial size of the boot class loader data _metaspace") _ _- _ product(bool, TraceGen0Time, _false, _ "Trace accumulated time for Gen 0 _collection") _ __ ------------ I prefer "B" . Because, I guess many users think MetaspaceSize decides initial metaspace size. If my idea is correct, I will file this to JBS and upload patch to webrev. Please only correct the description of MetaspaceSize. Jon Thanks, Yasumasa

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