Major Clojure 1.10 performance degredation on JDK11

Rob Browning rlb at
Sun Feb 10 08:30:16 GMT 2019

Alex Miller <alex at> writes:

> If not, why not?

It was originally caused by a bug in dh_strip_nondeterminism which is
part of Debian's work toward reproducible builds

Of course it'll be much better if/when projects are just reproducible
upstream as a matter of course, but my understanding is that's still
quite a way off.

> I think it's almost certainly this issue with clj / class timestamps.
> afaik, nothing was ever filed about this in the Clojure ticket system.

Makes sense -- It wasn't a Clojure issue.  The debhelper bug was fixed,
and still apears to be, at least with respect to Debian's 1.8 package:

  $ dpkg --status clojure1.8 | grep Version
  Version: 1.8.0-8

  $ time clojure1.8 -e ''

  real    0m0.537s
  user    0m1.088s
  sys     0m0.060s

Offhand I'd guess that either there's just some new issue, or perhaps
there are jars that were built with the older version of
dh_strip_notdeterminism lingering and getting in the way somehow.

For what it's worth, I think the fix did something to make it so that
the class timestamps would be at least a second newer than the clj
timestamps (while still deterministic), and if I recall correctly, Chris
Lamb came up with the fix.

Rob Browning
rlb and
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