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<div class="moz-cite-prefix">On 2/25/16 10:23 AM, Chris Plummer
wrote:<br>
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<blockquote cite="mid:56CF46B4.9080800@oracle.com" type="cite">
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<div class="moz-cite-prefix">On 2/22/16 8:19 AM, Chris Plummer
wrote:<br>
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<blockquote cite="mid:56CB3524.7030800@oracle.com" type="cite">
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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>
</div>
<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>
</div>
<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>
</blockquote>
Updated webrev:<br>
<br>
<a moz-do-not-send="true" class="moz-txt-link-freetext"
href="http://cr.openjdk.java.net/%7Ecjplummer/8146436/webrev.03/">http://cr.openjdk.java.net/~cjplummer/8146436/webrev.03/</a><br>
<br>
thanks,<br>
</blockquote>
Ping. Tom and Jon can you give final approval for this?<br>
<br>
Thanks.<br>
<br>
Chris<br>
<blockquote cite="mid:56CF46B4.9080800@oracle.com" type="cite"> <br>
Chris<br>
<br>
<blockquote cite="mid:56CB3524.7030800@oracle.com" type="cite">
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>
</div>
<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>
</div>
<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>
</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>
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