RFR: 8353787: Increased number of SHA-384-Digest java.util.jar.Attributes$Name instances leading to higher memory footprint

[Sean Mullan]

On Mon, 7 Apr 2025 06:34:11 GMT, Jaikiran Pai <jpai at openjdk.org> wrote:

> Can I please get a review of this change which proposes to address the increase in memory footprint of an application that uses signed JAR files, signed with `SHA-384` digest algorithm? This addresses https://bugs.openjdk.org/browse/JDK-8353787.
> 
> As noted in that issue and the linked mailing list discussion, it has been noticed that when JARs signed with `SHA-384` digest algorithm (which is the default since Java 19) are loaded, the number of `java.util.Attributes$Name` instances held in memory increase, leading to an increase in the memory footprint of the application.
> 
> The `Attributes` class has an internal cache which is meant to store `Name` instances of some well-known manifest attributes. It already has the `Name` instances for `SHA1-Digest` and `SHA-256-Digest` manifest attributes cached, but is missing an entry for `SHA-384-Digest`. The commit in this PR adds `SHA-384-Digest` to that cache.
> 
> Given the nature of this change, no new jtreg test has been introduced and existing tests in tier1, tier2 and tier3 continue to pass with this change. I've manually verified that this change does reduce the memory footprint of an application which has signed JARs with `SHA-384` digest algorithm  (details in a comment of this PR).

I suggest making this a P3 since it sounds like it would be useful to backport to 21.

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Marked as reviewed by mullan (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/24475#pullrequestreview-2746704222