Thank you for reporting this issue and providing the details. I have
created https://bugs.openjdk.org/browse/JDK-8353787 to track this. Any
fixes done related to this issue will be first done against the mainline
JDK and the project members that manage the update releases
(https://openjdk.org/projects/jdk-updates/) will then decide if/when
this change should be backported.
-Jaikiran
On 04/04/25 11:55 pm, Ayman wrote:
Yes, I started looking into this because of a memory regression.
While upgrading our project from Java 17 to Java 21, I noticed an
increase in memory consumption. After dumping the heap and analyzing
the differences, I found that there are a few thousand instances of
the class "java.util.jar.Attributes$Name" which all contain the same
string which is "SHA-384-Digest".
In our case, it was a 2MB increase in a process that uses 35MB
normally so that's almost a 5% increase.
The issue here is that we are loading multiple jars that each contain
a MANIFEST file which contains hundreds of classes and so many times
the string "SHA-384-Digest".
It would be nice if the fix could be backported to java 21 since it's
the current LTS that's impacted.
On Fri, Apr 4, 2025 at 7:07 PM Jaikiran Pai <jai.forums2...@gmail.com>
wrote:
The caching of some attribute names in the java.util.jar.Attributes
class appears to have been introduced in
https://bugs.openjdk.org/browse/JDK-6805750 (RFR
https://mail.openjdk.org/pipermail/core-libs-dev/2018-April/052697.html).
Given the precedence, it may be OK to add "SHA-384-Digest" to that
set,
but I don't know how much (if any) would it help with the
performance.
Did you happen to notice any performance issues which prompted you to
look at this cache?
-Jaikiran
On 04/04/25 10:25 pm, Jaikiran Pai wrote:
> Since this is about caching values in the java.util.jar.Attributes
> class, the discussion is more appropriate in the core-libs-dev
mailing
> list. I've added it to the "To" now and "Bcc"ed the jdk-dev mailing
> list. Please subscribe to core-libs-dev
> https://mail.openjdk.org/mailman/listinfo/core-libs-dev if you
haven't
> already and we can continue the discussion there.
>
> -Jaikiran
>
> On 04/04/25 8:54 pm, Ayman wrote:
>> Hello,
>>
>> Starting from JDK 19, SHA-384 is replacing SHA-256 as the default
>> digest algorithm in the jarsigner:
>> https://bugs.openjdk.org/browse/JDK-8283475
>>
>> This means that the string "SHA-384" is now written multiples
times
>> is the MANIFEST files, this has been tackled in the past by adding
>> the string "SHA-256" as a KNOWN_NAME that shouldn't be
duplicated in
>> memory:
>>
https://github.com/openjdk/jdk/blob/master/src/java.base/share/classes/java/util/jar/Attributes.java#L729
>>
>>
>> Is it possible to do the same with "SHA-384"?
>>
>> Thanks,
