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<div class="moz-cite-prefix">Hi Tom,<br>
<br>
if (!UseAggressiveHeapShrink) {<br>
// If UseAggressiveHeapShrink is false (the default),<br>
// we don't want shrink all the way back to initSize if
people call<br>
// System.gc(), because some programs do that between
"phases" and then<br>
// we'd just have to grow the heap up again for the next
phase. So we<br>
// damp the shrinking: 0% on the first call, 10% on the
second call, 40%<br>
// on the third call, and 100% by the fourth call. But if
we recompute<br>
// size without shrinking, it goes back to 0%.<br>
shrink_bytes = shrink_bytes / 100 * current_shrink_factor;<br>
}<br>
assert(shrink_bytes <= max_shrink_bytes, "invalid shrink
size");<br>
if (current_shrink_factor == 0) {<br>
_shrink_factor = 10;<br>
} else {<br>
_shrink_factor = MIN2(current_shrink_factor * 4, (size_t)
100);<br>
}<br>
<br>
I got rid of the changes at the start of the method, and added the
!UseAggressiveHeapShrink check and the comment, so the first 2
lines above and the closing right brace are now the only change in
the file, other than the copyright date. If you want I could also
move the _shrink_factor adjustment into this block since the value
of _shrink_factor becomes irrelevant if UseAggressiveHeapShrink is
true. The assert should remain outside the block.<br>
<br>
cheers,<br>
<br>
Chris<br>
<br>
On 2/10/16 12:16 PM, Tom Benson wrote:<br>
</div>
<blockquote cite="mid:56BB9A9A.7060901@oracle.com" type="cite">
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Hi Chris,<br>
OK, that all sounds good. <br>
<br>
>> I can change it, although that will mean filing a new
CCC.<br>
Ah, I'd forgotten about that. Not worth it, unless there's a
landslide of support for a different name.<br>
<br>
Tnx,<br>
Tom<br>
<br>
<div class="moz-cite-prefix">On 2/10/2016 3:06 PM, Chris Plummer
wrote:<br>
</div>
<blockquote cite="mid:56BB9831.5030504@oracle.com" type="cite">
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http-equiv="Content-Type">
<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
<meta http-equiv="content-type" content="text/html;
charset=utf-8">
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. 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 moz-do-not-send="true"
class="moz-txt-link-freetext"
href="http://cr.openjdk.java.net/%7Ecjplummer/8146436/webrev.02/">http://cr.openjdk.java.net/~cjplummer/8146436/webrev.02/</a>
<br>
Bug: <a moz-do-not-send="true"
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>
<br>
</blockquote>
<br>
</blockquote>
<br>
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