<html>
<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<br>
<br>
<div class="moz-cite-prefix">On 6/3/2015 1:00 PM, Jeremy Manson
wrote:<br>
</div>
<blockquote
cite="mid:CAPYFHW1r9PxrOPEQwM4ugM5RY8_jvBnR_h5HL0uk5cpt2LYL+A@mail.gmail.com"
type="cite">
<div dir="ltr">I'm not on hotspot-gc-dev, so I'm not seeing the
responses. But I looked online...
<div><br>
</div>
<div>Jon says that "My understanding was that the change was
based on a parallelization of the serial mark-sweep-compact
(used by CMS for full collections). If it was based on the
parallel-old compaction used by ParallelGC, then my bad. It
should have been reviewed."</div>
<div><br>
</div>
<div>His original understanding was correct - we parallelized
the serial mark-sweep-compact used by CMS. I'm sorry if I
misled anyone there.</div>
</div>
</blockquote>
<br>
No problem. It gave me a chance to say again that <br>
I'd rather not have to support two implementations of <br>
a parallel full stop-the-world collector. We have that<br>
issue with the two implementations of a parallel young <br>
collector and I'd really rather not go there again.<br>
<br>
<blockquote
cite="mid:CAPYFHW1r9PxrOPEQwM4ugM5RY8_jvBnR_h5HL0uk5cpt2LYL+A@mail.gmail.com"
type="cite">
<div dir="ltr">
<div><br>
<div>Otherwise, thanks for your thoughtful reply, Volker. In
my experience of open source projects, if you can't get a
maintainer to agree to consider your patch, then there is
really very little that you can do. And I totally get that
maintainers don't want / have the time for the burden of
understanding huge amounts of complicated code they didn't
write!</div>
</div>
<div><br>
</div>
<div>So, the question comes down to what "community supported"
means in this case. We can't actually submit anything to
Hotspot without approval from someone within Oracle. We have
a vested interest in keeping this patch working, but, for
major JDK releases, we really only start stress testing to
identify problems with it when we upgrade to the latest
versions of the JDK, which usually happens some months after
Oracle releases it. That could cause some issues for
upstream.</div>
<div><br>
</div>
<div>The upside is that I think we'd be willing to do what it
takes, if getting it upstreamed is a possibility. This patch
is a huge nuisance, and it is much simpler not to have to do a
week or two's worth of forward porting every year. And
whatever problems arise are problems that we have to fix
anyway.</div>
<div><br>
</div>
<div>Jon, if you are particularly worried, note that we can keep
it hidden behind a flag without too much difficulty (and did
for a year or two).</div>
</div>
</blockquote>
<br>
I don't think that helps much. Unless Google is willing to own any<br>
bug reports that come in on CMS when it is turned on. My main<br>
concern is long term support. And whether we would have to<br>
do our testing with it both turned on and turned off. Both those<br>
seem like a big commitment on Oracle's part. Only my opinion,<br>
of course.<br>
<br>
Jon<br>
<br>
<blockquote
cite="mid:CAPYFHW1r9PxrOPEQwM4ugM5RY8_jvBnR_h5HL0uk5cpt2LYL+A@mail.gmail.com"
type="cite">
<div dir="ltr">
<div><br>
</div>
<div>Jeremy</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Wed, Jun 3, 2015 at 2:32 AM, Volker
Simonis <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:volker.simonis@gmail.com" target="_blank">volker.simonis@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">
<div>
<div>
<div>Hi Jeremy,<br>
<br>
</div>
thanks for your answer. Maybe you misunderstood Ivan
but it is definitely his and our (i.e. SAP's)
intention to make this part of the OpenJDK.<br>
<br>
</div>
I can also fully understand the pains you have with
integrating changes into the HotSpot. We've gone through
this painful process with our ppc64 port a year ago but
we think it will finally pay off. After all you (i.e.
Google) used it as the base for your ppc64le port
(Alexander Smundak contributed most of the LE-specific
changes).<br>
<br>
We're facing the exactly same problems regarding the
support of proprietary changes in a downstream version
of the OpenJDK. That was actually the main reason why we
started contributing to the OpenJDK. What we want to
kindly ask you is to make your changes and extensions
more transparently visible to the community if you
intend to integrate them into the OpenJDK. If Hiroshi
had posted his changes directly to the hotspot mailing
lists instead of sending them privately to Jon I'm
pretty sure we would have picked them up. And maybe
together we would have managed to push them through (we
have some reviewers as well :). After all, there are
already quite a lot of features in the OpenJDK which are
supported and maintained by the community (i.e. RedHat,
IBM, SAP, ...) and not by Oracle. <br>
<br>
</div>
I don't have much experience with other Open Source
projects, but with OpenJDK and especially HotSpot it's
pretty pointless to try to contribute something by writing
mails like "..I've implemented this cool feature XXX. If
somebody is interested I can post more details..". You'll
almost never get any feedback to such kind of requests.
You'll at least have to post a complete buildabel and
runnable patch against the head revision. I know that's a
lot of overhead and we're having this very same discussion
if it is worth doing it nearly every day for most of the
features/additions we are implementing. Nevertheless, I
think it is worth doing it although it sometimes may take
years until you get your changes back in the version you
are using productively.<br>
<div><br>
</div>
<div>So coming back to Ivan's initial request, we would
kindly ask you to just publish your changes in their
current form against your current version (8u45 or
whatsoever). We'll take a look at them an may invest
some time and effort (also jointly with you if desired)
to forward port them to 9 and propose them for
integration into the head revision if that makes sense.
Thus that sound reasonable to you?<br>
</div>
<div><br>
</div>
<div>Thank you and best regards,<br>
</div>
<div>Volker<br>
<br>
</div>
</div>
<div class="HOEnZb">
<div class="h5">
<div class="gmail_extra"><br>
<div class="gmail_quote">On Tue, Jun 2, 2015 at 5:00
PM, Jeremy Manson <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:jeremymanson@google.com"
target="_blank">jeremymanson@google.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">We'd much rather it be part of
OpenJDK, because it is large and fairly
complicated, so that would save us time and
energy forward porting it every year or so.
It's pretty large (for 8u45, it is a 2600 line
change and touches 20 files), so it tends to be
a lengthy and complicated forward port. We
would much rather spend that time doing
something more interesting.
<div><br>
</div>
<div>Just posting an updated patch whenever we
need to update it would be a little annoying
(although not impossible).
<div><br>
</div>
<div>Hiroshi Yamauchi tried to offer it to (I
think it was) Jon Masamitsu a few years ago,
and Jon didn't know anyone with the
bandwidth to review it. (It was around the
same time we contributed the parallel
initial mark). I believe that was when CMS
was unowned for a while. Perhaps there's a
different story now? Oracle volunteers?
<div>
<div><br>
<div>(Procedural: One problem is that
Hotspot reviews have to go through
someone at Oracle. We had it written
by an OpenJDK author and reviewed by a
reviewer. We've been using it in
production for years without too many
headaches (although we have yet to
inflict^Wlaunch 8u45, which has the
latest updates, widely). I totally
understand that Oracle folks are the
ones who have to pay the price for a
bad check-in, but it's a pretty big
hurdle for us.)</div>
<span><font color="#888888">
<div><br>
</div>
<div>
<div>
<div>Jeremy<br>
</div>
</div>
</div>
</font></span></div>
</div>
</div>
</div>
</div>
<div>
<div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Tue, Jun 2, 2015
at 6:12 AM, Galkin, Ivan <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:ivan.galkin@sap.com"
target="_blank">ivan.galkin@sap.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="margin:0 0 0 .8ex;border-left:1px
#ccc solid;padding-left:1ex">
<div link="blue" vlink="purple"
lang="EN-GB">
<div>
<p class="MsoNormal"><span lang="DE">Hi,</span></p>
<p class="MsoNormal"><span lang="DE"> </span></p>
<p class="MsoNormal">in the thread
„JEP 248: Make G1 the Default
Garbage Collector” [1] there is an
email from Jeremy Manson, who
mentions the enhancements made by
Google to improve CMS.</p>
<p class="MsoNormal">Especially the
parallelizing of full compaction
is a great improvement and we at
SAP see the strong demand of it.</p>
<p class="MsoNormal"> </p>
<p>@Jeremy: Are these changes
published somewhere? May we have
insight into the diffs you've
made? We could collaborate in
order to try to bring your changes
into OpenJDK.</p>
<p> </p>
<p>Kind regards and thank you in
advance,</p>
<p>Ivan</p>
<p> </p>
<p>[1] <a moz-do-not-send="true"
href="http://mail.openjdk.java.net/pipermail/hotspot-dev/2015-June/018740.html"
target="_blank">
http://mail.openjdk.java.net/pipermail/hotspot-dev/2015-June/018740.html</a></p>
</div>
</div>
</blockquote>
</div>
<br>
</div>
</div>
</div>
</blockquote>
</div>
<br>
</div>
</div>
</div>
</blockquote>
</div>
<br>
</div>
</blockquote>
<br>
</body>
</html>