New CML option to adjust storage of extra startup hints

#1433

New parameter 'extraStartupHints` added to the -Xshareclasses topic.

Closes #1433
Signed-off-by: Sreekala Gopakumar [email protected]

docs/version0.49.md

@@ -27,6 +27,7 @@ The following new features and notable changes since version 0.48.0 are included
 
 - [New binaries and changes to supported environments](#binaries-and-supported-environments)
 - [Change to the shared classes cache generation number](#change-to-the-shared-classes-cache-generation-number)
+- [New shared classes cache suboption added to adjust the number of startup hints that can be stored](#new-shared-classes-cache-suboption-added-to-adjust-the-number-of-startup-hints-that-can-be-stored)
 
 ## Features and changes
 
@@ -46,6 +47,12 @@ To save space, all existing shared caches can be removed unless they are in use
 
 The shared classes cache generation number is modified because of a change in the format of ROMClasses that are stored in the shared classes cache. A new flag `J9AccClassIsShared` is added to ROMClasses to indicate whether a ROMClass was loaded from a shared classes cache or from a VM.
 
+### New shared classes cache suboption added to adjust the number of startup hints that can be stored
+
+You can use the `-Xshareclasses:extraStartupHints=<number>` option to adjust the number of startup hints that can be stored in a shared cache. By default, you can store only up to 64 startup hints in a shared cache.
+
+For more information, see [`-Xshareclasses:extraStartupHints`](xshareclasses.md#extrastartuphints).
+
 ## Known problems and full release information
 
 To see known problems and a complete list of changes between Eclipse OpenJ9 v0.48.0 and v0.49.0 releases, see the [Release notes](https://github.com/eclipse-openj9/openj9/blob/master/doc/release-notes/0.49/0.49.md).

docs/xshareclasses.md

@@ -239,6 +239,16 @@ case, the VM continues without using shared classes.
 
 : Destroys all caches that are unused for the time that is specified before loading shared classes. This option is not a utility option because it does not cause the VM to exit. On Windows systems, which have NTFS file systems, the `expire` option is accurate to the nearest hour.
 
+### `extraStartupHints`
+
+        -Xshareclasses:extraStartupHints=<number>
+
+: where, \<number\> is greater than or equal to 0.
+
+: Adjusts the number of startup hints that can be stored in a shared cache. By default, you can store only up to 64 startup hints in a shared cache. This count decrements by 1 each time a startup hint is stored. After the count reaches 0, no more hints can be added to the cache. You can use `-Xshareclasses:extraStartupHints=<number>` to adjust this count as needed. For example, `-Xshareclasses:extraStartupHints=0` prevents any new hints to be stored and `-Xshareclasses:extraStartupHints=10` allows 10 more new hints in addition to the default number of 64 startup hints.
+
+You can use [`-Xshareclasses:printStats=startuphint`](#printstats-cache-utility) to check how many startup hints are already stored in the shared cache or `-Xshareclasses:printDetails` to check how many more hints can be stored in the cache.
+
 ### `fatal`
 
         -Xshareclasses:fatal