-
Notifications
You must be signed in to change notification settings - Fork 0
Features Contributed by SAP
This page lists features of SapMachine that were crafted by SAP to enhance the enterprise-readiness of SapMachine. In general, we contribute these directly upstream to OpenJDK. We might downport these to an earlier version of SapMachine, though. If a feature is not accepted by the OpenJDK community, but considered essential by us, it might only appear in SapMachine. This listing omits bug fixes, work on our platform ports, work on the build and test infrastructure etc. we do directly in OpenJDK.
The Metaspace memory region contains metadata for loaded java classes. It can get abnormally large and is a common cause for high memory footprint and Java OOMs, especially when running programs with many class loaders (e.g. JEE), lots of reflection or lambdas.
SAP did significant work in improving the Metaspace allocator. We greatly reduced its memory footprint and made it more predictable. Additionally, we contributed a large number of smaller fixes and improvements.
| OpenJDK | SapMachine | |
|---|---|---|
| 8198423: Improve metaspace chunk allocation | 11 | 11 |
Applications run in Containers or the Cloud need to be optimized for small footprint.
| OpenJDK | SapMachine | |
|---|---|---|
|
8198510: Enable UseDynamicNumberOfGCThreads by default We saw the VM starting too many GC threads. |
11 | 11 |
|
8198756: Lazy allocation of compiler threads We saw the VM starting too many compiler threads. |
11 | 11 |
|
8213086: Compiler thread creation should be bounded by available space in memory and Code Cache We saw the VM starting too many compiler threads. |
11.0.3 | 11.0.2 |
|
8196062: Enable docker container related tests for linux ppc64le This also needed some functional improvements. |
11 | 11 |
| 8197412: Enable docker container related tests for linux s390x | 11 | 11 |
| OpenJDK | SapMachine | |
|---|---|---|
| 8170868: DefaultProxySelector should use system defaults on Windows, MacOS and Gnome | 9 | 9 |
| 8213082: (zipfs) Add support for POSIX file permissions | 13?? | 11.0.2 |
| OpenJDK | SapMachine | |
|---|---|---|
| 8215962: Support ThreadPriorityPolicy mode 1 for non-root users on linux/bsd | 13 | 11.0.2 |
Configuring stack sizes used to depend strongly on the system page size and was optimized for 4K pages. We made stack configuration less dependent on the page size wrt. overflow detection and minimal stack sizes.
| OpenJDK | SapMachine | |
|---|---|---|
| 8170655: [posix] Fix minimum stack size computations | 10 | 10 |
| 8139864: Improve handling of stack protection zones. | 10 | 10 |
Many exceptions thrown in OpenJDK 10 and earlier don't give detailed information about the underlying problem, although it's known when the exception is thrown. We improve these messages step by step.
SAP JVM was known for its debugging on demand. This means you could attach at any time to an application running on SAP JVM and start debugging it. We want to enhance OpenJDK with similar features.
| OpenJDK | SapMachine | |
|---|---|---|
| 8214892: Delayed starting of debugging via jcmd | 11.0.3 | 11.0.2 |
| These changes improve the VM performance if debugging is enabled: | ||
| 8214352: C1: Unnecessary "compilation bailout: block join failed" with JVMTI | 13 | 11.0.2 |
Jcmd allows to request information from a running Java VM. SAP JVM knows similar tools. We add the commands known in the SAP JVM tools to Jcmd.
| OpenJDK | SapMachine | |
|---|---|---|
| 8189864: Provide an ascii map to visualize metaspace fragmentation | 10 | 10 |
|
8198691: CodeHeap State Analytics Print information about the memory containing Java methods compiled to native code. |
11 | 11 |
|
8198553: jcmd: separate Metaspace statistics from NMT Introduces new command VM.metaspace. |
11 | 11 |
| 8201572: Improve Metaspace Statistics | 11 | 11 |
| 8203219: VM.metaspace jcmd should optionally show loaded classes for loaders | 11 | 11 |
| 8203455: jcmd: VM.metaspace: print loader name for anonymous CLDs | 11 | 11 |
| 8203682: Add jcmd "VM.classloaders" command to print out class loader hierarchy, details | 11 | 11 |
| 8200720: Print additional information in thread dump (times, allocated bytes etc.) | 11 | 11 |
| 8203682: Add jcmd "VM.classloaders" command to print out class loader hierarchy, details | 11 | 11 |
| 8203343: VM.{metaspace|classloaders|classhierarchy...} jcmd should show invocation targets for Generated{Method|Constructor}AccessorImpl classes | 11 | 11 |
We will improve Java Flight Recorder and Mission Control as a replacement of SAP JVM Profiler.
| OpenJDK | SapMachine | |
|---|---|---|
| 8207392: [PPC64] Implement JFR profiling. | 11 | 11 |
| 8211768: [s390] Implement JFR profiling. | 11.0.2 | 11.0.2 |
If OpenJdk crashes, it writes a collection of basic information into a file named hs-err_<process id>.log. This information is very useful to analyze the crash post-mortem. We enrich this printout with information we found useful for SAP JVM support.
| OpenJDK | SapMachine | |
|---|---|---|
| 8191101: Show register content in hs-err file on assert | 11 | 11 |
| 8203292: Print complete set of flags in the hs_err file | 11 | 11 |
| 8202427: Enhance os::print_memory_info on Windows | 11 | 11 |
| 8204476: Add additional statistics to CodeCache::print_summary | 11 | 11 |
| 8204477: Count linkage errors and print in Exceptions::print_exception_counts_on_error | 11 | 11 |
| 8204598: Add more thread-related system settings info to hs_error file on Linux | 11 | 11 |
| 8210964: Add more ld preloading info to hs_error file on Linux | 11.0.2 | 11.0.2 |
| 8211852: Inspect stack during error reporting Besides this functional improvement, we contributed 8210754 to make printing register content more reliable. | 11.0.2 | 11.0.2 |
| OpenJDK | SapMachine | |
|---|---|---|
| 8204539: improve error messages in matchJavaTZ [windows] | 11 | 11 |
We improve the documentation, be it Javadoc, the tools etc.
| OpenJDK | SapMachine | |
|---|---|---|
| 8200384: jcmd help output should be sorted | 11 | 11 |
| 8189102: All tools should support -?, -h and --help | 11 | 11 |
| 8203014: jcmd should output command list if no command is given | 11 | 11 |