On 2018-12-04 08:42, Alan Bateman wrote:
On 03/12/2018 16:50, Claes Redestad wrote:
:
The extra Names added to KNOWN_NAMES was my doing, and it was based
on commonly used attributes in Jar file manifests scanned from a set
commonly used applications as an alternative to building up a Name
cache dynamically (which is frought with other perils). The chose
extras gave a marginal but measurable improvement in startup to a
wide array of applications as a result, and their inclusion is
strictly an internal implementation detail. If you insist on having
them removed I won't object, but I believe it's an harmless
optimization.
There are several non-standard and tool/library specify attribute name
in this list, many should not be interesting to libraries on either
the class path or module path. So I think we should look at pruning
that list. Ideally it would like just standard and JDK-specific
attributes as they are the only attributes that the JDK knows about.
These non-standard and tool/library specific names appear in the
manifest of a great many jar files, for example on maven central, and
including the most common non-standard manifest attributes significantly
reduce allocation churn reading such manifests. Especially true for ones
that were oft repeated within the same manifest, e.g.,"Name" and
"SHA1-Digest" for signed entries.
Was it a crucial optimization? Probably not, a few percent on some
startup applications.
Ideals vs trade-offs... Hard-coding a bunch of arbitrarily chosen
external values isn't exactly pretty, sure, but I do think the JDK
should try to optimize for typical behavior, and the fact that many
(most?) libraries on maven central have OSGi attributes ("Bundle-*") in
their manifests is one such typical behavior, and this optimization was
very low cost and net beneficial on most. With 8214712 the overhead cost
is even less (almost zero in fact).
/Claes
