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<div class="moz-cite-prefix">On 2/18/16 7:21 AM, Tom Benson wrote:<br>
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<blockquote cite="mid:56C5E177.9030104@oracle.com" type="cite">
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Hi Chris,<br>
<br>
<div class="moz-cite-prefix">On 2/10/2016 3:53 PM, Chris Plummer
wrote:<br>
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<blockquote cite="mid:56BBA353.2020805@oracle.com" type="cite">
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<div class="moz-cite-prefix">On 2/10/16 12:50 PM, Tom Benson
wrote:<br>
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<blockquote cite="mid:56BBA27C.2080106@oracle.com" type="cite">
<br>
I've heard from another GC team person that there might be
more feedback on the name coming, after some discussion. Not
sure if it will constitute the 'landslide' I mentioned. 8^)<br>
</blockquote>
No problem. I'll wait for that to settle before sending out a
final webrev.<br>
</blockquote>
<br>
"Landslide" may not be the right term, but there was mild
consensus among the GC team that it's worth going through CCC
again to replace UseAggressiveHeapShrink. Our suggestion is
"ShrinkHeapInSteps", which would be on by default, and hopefully
describes what's happening without any other implications. So
you'd disable it to get what you want.<br>
Tom<br>
</blockquote>
Hi Tom,<br>
<br>
Ok, I'll get started with this. Just got back from vacation today,
but it shouldn't take long to get to it.<br>
<br>
thanks,<br>
<br>
Chris<br>
<blockquote cite="mid:56C5E177.9030104@oracle.com" type="cite"> <br>
<blockquote cite="mid:56BBA353.2020805@oracle.com" type="cite"> <br>
thanks,<br>
<br>
Chris<br>
<blockquote cite="mid:56BBA27C.2080106@oracle.com" type="cite">
Tom<br>
<br>
<div class="moz-cite-prefix">On 2/10/2016 3:39 PM, Chris
Plummer wrote:<br>
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<blockquote cite="mid:56BB9FEA.5070506@oracle.com" type="cite">
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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>
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<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>
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<blockquote cite="mid:56BB9831.5030504@oracle.com"
type="cite">
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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>
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<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>
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