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On 2012-01-20 17:46, Bengt Rutisson wrote:
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Stefan,<br>
<br>
Thanks for the prompt review!<br>
<br>
Comments inline.<br>
<br>
On 2012-01-20 17:21, Stefan Karlsson wrote:
<blockquote
cite="mid:8C7CE33B-1215-4828-836B-EC0860F5D5CF@oracle.com"
type="cite">
<div><span class="Apple-style-span"
style="-webkit-tap-highlight-color: rgba(26, 26, 26,
0.296875); -webkit-composition-fill-color: rgba(175, 192,
227, 0.230469); -webkit-composition-frame-color: rgba(77,
128, 180, 0.230469); ">On 20 jan 2012, at 17:06, Bengt
Rutisson <<a moz-do-not-send="true"
href="mailto:bengt.rutisson@oracle.com">bengt.rutisson@oracle.com</a>>
wrote:</span><br>
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<div><br>
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<span>Hi all,</span><br>
<span></span><br>
<span>Can I have a couple of quick reviews for this small
change:</span><br>
<span><a moz-do-not-send="true"
href="http://cr.openjdk.java.net/%7Ebrutisso/7131791/webrev.02">http://cr.openjdk.java.net/~brutisso/7131791/webrev.02</a></span><br>
<span></span><br>
<span>This should hopefully fix the 500+ failures in the G1
nightlies. So, I would like to get it in before the
nightlies tonight.</span><br>
<span></span><br>
<span>The issue is that we call collect() which will trigger
a collection without protecting the memory that we just
allocated for a humongous object. The fix (thanks Tony for
helping me out!!!) is to fake an object and create a
handle to it before we call collect.</span><br>
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<pre><font class="Apple-style-span" face="Helvetica"><span class="Apple-style-span" style="white-space: normal;"><span class="changed">1067 Handle h((oop)result);</span> </span></font></pre>
<pre><font class="Apple-style-span" face="Helvetica"><span class="Apple-style-span" style="white-space: normal;">1068 collect(GCCause::_g1_humongous_allocation); </span></font></pre>
<pre><font class="Apple-style-span" face="Helvetica"><span class="Apple-style-span" style="white-space: normal;">1069 } </span></font></pre>
<pre><font class="Apple-style-span" face="Helvetica"><span class="Apple-style-span" style="white-space: normal;">1070 return result; </span></font></pre>
<pre><font class="Apple-style-span" face="Helvetica"><span class="Apple-style-span" style="white-space: normal;">1071 }</span></font></pre>
<pre><font class="Apple-style-span" face="Helvetica"><span class="Apple-style-span" style="white-space: normal;">Can we really have a handle to uninitialized memory?</span></font></pre>
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The memory is not uninitialized since I fake an object there with
the call to CollectedHeap::fill_with_object(result, word_size,
false); just before the code you have above.<br>
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I missed that.<br>
<br>
<blockquote cite="mid:4F199A60.6070506@oracle.com" type="cite"> <br>
<blockquote
cite="mid:8C7CE33B-1215-4828-836B-EC0860F5D5CF@oracle.com"
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<pre><font class="Apple-style-span" face="Helvetica"><span class="Apple-style-span" style="white-space: normal;">Are you sure that the humongous object will not be moved by a full collection. You should probably return h() instead of result.</span></font></pre>
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Humongous objects will not be moved by G1 collections so I think
we are ok.<br>
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OK. But maybe we should be a bit defensive and return h() here.<br>
<br>
StefanK<br>
<br>
<blockquote cite="mid:4F199A60.6070506@oracle.com" type="cite"> <br>
Thanks for the prompt review!<br>
<br>
Bengt<br>
<blockquote
cite="mid:8C7CE33B-1215-4828-836B-EC0860F5D5CF@oracle.com"
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<pre><font class="Apple-style-span" face="Helvetica"><span class="Apple-style-span" style="white-space: normal;">
</span></font></pre>
<pre><font class="Apple-style-span" face="Helvetica"><span class="Apple-style-span" style="white-space: normal;">StefanK</span></font></pre>
<br>
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<span>Bengt</span><br>
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