PTAL<br><a href="http://cr.openjdk.java.net/~rasbold/8061259/webrev.02/" target="_blank" style="font-family:arial,sans-serif;line-height:19.5px">http://cr.openjdk.java.net/~rasbold/8061259/webrev.02/</a><br><div><br></div><br><div class="gmail_quote">On Thu Oct 30 2014 at 12:28:19 AM Bengt Rutisson <<a href="mailto:bengt.rutisson@oracle.com">bengt.rutisson@oracle.com</a>> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<br>
Hi again,<br>
<br>
One more minor thing.<br>
<br>
The methods has_promotion_failed(), set_promotion_failed() and
reset_promotion_failed() are protected but they could be made
private instead.<br>
<br>
Thanks,<br>
Bengt</div><div bgcolor="#FFFFFF" text="#000000"><br>
<br>
<div>On 2014-10-30 08:09, Bengt Rutisson
wrote:<br>
</div>
<blockquote type="cite">
<br>
<br>
Hi Jungwoo,<br>
<br>
<div>On 2014-10-29 23:51, Jungwoo Ha
wrote:<br>
</div>
<blockquote type="cite">
<div class="gmail_quote">
<div>PTAL </div>
<div><a href="http://cr.openjdk.java.net/%7Erasbold/8061259/webrev.01/" style="line-height:19.7999992370605px" target="_blank">http://cr.openjdk.java.net/~rasbold/8061259/webrev.01/</a><br>
</div>
<div><br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">I've looked a bit at
the webrev. A couple of comments:<br>
</div>
<div bgcolor="#FFFFFF" text="#000000"> <br>
Why do you use OrderAccess methods for writing and reading
the _has_promo_failed flag in has_promo_failed() and
set_promot_failed() ?<br>
</div>
</blockquote>
<div><br>
</div>
</div>
<div class="gmail_quote">
<div>I think that has no effect on x86, but I assumed that
processors with weak memory model may want ordering of
set/reset/has call.</div>
</div>
</blockquote>
<br>
You don't need the OrderAccess methods for the weak memory models
here either. You just race on reading the variable and if you see
the "wrong" value you eventually take a lock (which will order all
memory accesses) to read the variable properly.<br>
<br>
By removing the use of OrderAccess you can make
ConcurrentMarkSweepGeneration::_has_promotion_failed a bool
instead of a juint which simplifies the code a bit.<br>
<br>
<blockquote type="cite">
<div class="gmail_quote">
<div><br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">Can we write out the
full word "promotion" instead of just "promo" in the
variables and methods?<br>
</div>
</blockquote>
<div><br>
</div>
</div>
<div class="gmail_quote">
<div>Done.</div>
</div>
<div class="gmail_quote">
<div><br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000"> Can we change the
name of the flag from UseCMSFastPromotionFailure to
CMSFastPromotionFailure? Most CMS flags start with CMS and
I don't think we need the "Use" prefix.<br>
</div>
</blockquote>
<div><br>
</div>
</div>
<div class="gmail_quote">
<div>Done.</div>
</div>
<div class="gmail_quote">
<div><br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">What do you think
about making the flag true by default? At least for JDK 9.
If we decide to backport to JDK 8 or 7 it might be a good
idea to keep the default value as false.<br>
</div>
</blockquote>
<div><br>
</div>
</div>
<div class="gmail_quote">
<div>Done.</div>
<div>Let me know if there is anything for me to do to backport
to JDK8 and 7.</div>
</div>
</blockquote>
<br>
I think this fix would be worth backporting to JDK 8. I don't
think there is much action required on your side. I created a
backport bug for JDK 8 just to make sure that we don't forget it.
It will be a little while before the 8 update repos are in a state
to accept enhancements again. So, it is nice to have the backport
bug to keep track of this.<br>
<br>
Backporting to JDK 7 requires some more work. Unless you have good
arguments for why it is important to backport this to JDK 7 I
don't think it is worth doing.<br>
<br>
<blockquote type="cite">
<div class="gmail_quote">
<div><br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">Did you find the
information provided by _fast_promo_failure_hitcount
useful for debugging? If it not too useful I would
consider removing it since it is cluttering up the code a
bit.</div>
</blockquote>
<div><br>
</div>
</div>
<div class="gmail_quote">
<div>I removed it.</div>
<div>It was useful to for development, but I think it is no
longer needed.</div>
</div>
</blockquote>
<br>
Great. Thanks.<br>
<br>
One more comment. This code comment appears in two places just
after we have taken the lock.<br>
<br>
3365 if (CMSFastPromotionFailure &&
has_promotion_failed()) {<br>
3366 // Caller must have checked already without
synchronization.<br>
3367 // Check again here while holding the lock.<br>
3368 return NULL;<br>
3369 }<br>
<br>
There is actually really no requirement that the caller must have
checked has_promotion_failed() before calling the method. That's
just an optimization. I think the first comment can be skipped and
we just leave the second comment "// Check again here while
holding the lock.". I would also suggest moving that comment up to
the line just before the if statement.<br>
<br>
Thanks,<br>
Bengt<br>
<br>
<br>
<blockquote type="cite">
<div class="gmail_quote">
<div><br>
</div>
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</blockquote>
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</div></blockquote></div>