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<div class="moz-cite-prefix">Hi Tom,<br>
<br>
Thanks for having a look. Comments inline below:<br>
<br>
On 2/10/16 11:27 AM, Tom Benson wrote:<br>
</div>
<blockquote cite="mid:56BB8F3D.3070502@oracle.com" type="cite">Hi
Chris,
<br>
My apologies if I missed the discussion somewhere, but is there a
specific rationale for adding this that can be mentioned in the
bug report? I can imagine scenarios where it would be useful, but
maybe the real need can be called out.
<br>
</blockquote>
In general, it is for customers that want to minimize the amount of
memory used by the java heap, and are willing to sacrifice some
performance (induce more frequent GCs) to save that memory. When
heap usage fluctuates greatly, the GC will tend to hold on to that
memory longer than needed due to the the current algorithm which
requires 4 full GCs before
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MaxHeapFreeRatio is fully honored. If this is what you are looking
for, I can add it to the CR.<br>
<blockquote cite="mid:56BB8F3D.3070502@oracle.com" type="cite">
<br>
I think it might be clearer if the new code in cardGeneration was
moved down to where the values are used. IE, I would leave the
inits of current_shrink_factor and _shrink_factor as they were at
lines 190/191. Â Then down at 270, just don't divide by the shrink
factor if UseAggressiveHeapShrink is set, and the updates to
shrink factor can be in the same conditional. This has the
advantage that you can fix the comment just above it to match this
special case. Do you think that would work?
<br>
</blockquote>
Yes, that makes sense. I'll get started on it. I have a vacation
coming up shortly, so what I'll get a new webrev out soon, but
probably will need to wait until after my trip to do more thorough
testing and push the changes.<br>
<blockquote cite="mid:56BB8F3D.3070502@oracle.com" type="cite">
<br>
It looks like the ending "\" at line 3330 in globals.hpp isn't
aligned, and the copyright in cardGeneration.cpp needs to be
updated.
<br>
</blockquote>
Ok.<br>
<blockquote cite="mid:56BB8F3D.3070502@oracle.com" type="cite">
<br>
One other nit, which you can ignore unless someone comes forward
to agree with me 8^) , is that I'd prefer the name
ShrinkHeapAggressively instead.  Maybe this was already debated
elsewhere....
<br>
</blockquote>
The name choice hasn't really been discussed or questioned. It was
what was suggested to me, so I stuck with it (The initial work was
done by someone else. I'm just getting it integrated into 9). I can
change it, although that will mean filing a new CCC.<br>
<br>
thanks,<br>
<br>
Chris<br>
<blockquote cite="mid:56BB8F3D.3070502@oracle.com" type="cite">Tom
<br>
<br>
On 2/4/2016 1:36 PM, Chris Plummer wrote:
<br>
<blockquote type="cite">Hello,
<br>
<br>
Please review the following for adding the -XX
UseAggressiveHeapShrink option. When turned on, it tells the GC
to reduce the heap size to the new target size immediately after
a full GC rather than doing it progressively over 4 GCs.
<br>
<br>
Webrev: <a class="moz-txt-link-freetext" href="http://cr.openjdk.java.net/~cjplummer/8146436/webrev.02/">http://cr.openjdk.java.net/~cjplummer/8146436/webrev.02/</a>
<br>
Bug: <a class="moz-txt-link-freetext" href="https://bugs.openjdk.java.net/browse/JDK-8146436">https://bugs.openjdk.java.net/browse/JDK-8146436</a>
<br>
<br>
Testing:
<br>
 -JPRT with '-testset hotspot'
<br>
 -JPRT with '-testset hotspot -vmflags
"-XX:+UseAggressiveHeapShrink"'
<br>
 -added new TestMaxMinHeapFreeRatioFlags.java test
<br>
<br>
thanks,
<br>
<br>
Chris
<br>
</blockquote>
<br>
</blockquote>
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