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Hi Vitaly,<br>
<br>
On 2012-03-23 14:45, Vitaly Davidovich wrote:
<blockquote
cite="mid:CAHjP37G7Gz7rE1f6nDxz982g4j_AECDw6ZSwdry1Zrb9i8NWPA@mail.gmail.com"
type="cite">
<p>Hi Bengt,</p>
<p>mutableNUMASpace line 99 has a small typo in the assert
message: "Remaining siz" should be "Remaining size".</p>
</blockquote>
<br>
Thanks for seeing it. Fixed.<br>
<br>
BTW, you don't have an OpenJDK username, right? If you consider this
a review I can list you as "Also-reviewed-by", when I push.<br>
<br>
Thanks,<br>
Bengt<br>
<br>
<blockquote
cite="mid:CAHjP37G7Gz7rE1f6nDxz982g4j_AECDw6ZSwdry1Zrb9i8NWPA@mail.gmail.com"
type="cite">
<p>Vitaly</p>
<p>Sent from my phone</p>
<div class="gmail_quote">On Mar 23, 2012 9:06 AM, "Bengt Rutisson"
<<a moz-do-not-send="true"
href="mailto:bengt.rutisson@oracle.com">bengt.rutisson@oracle.com</a>>
wrote:<br type="attribution">
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
Hi all,<br>
<br>
Could I have a couple of reviews for this change? This is on
the critical-watch list for hs23, so it would be great if I
could get some reviews already today.<br>
<br>
<a moz-do-not-send="true"
href="http://cr.openjdk.java.net/%7Ebrutisso/7103665/webrev.00/"
target="_blank">http://cr.openjdk.java.net/~brutisso/7103665/webrev.00/</a><br>
<br>
Some background:<br>
<br>
There are two problems that this fix solves:<br>
<br>
(1) When we run with -XX:+UseNUMA we have to make the heap
parsable since we leave some holes in the heap. We do this by
faking Integer arrays in those places. However, on a large
heap those holes can be larger than what can be covered by a
single Integer array. The fix is to allocate several arrays in
those cases.<br>
<br>
The easy fix would have been to call CollectedHeap::fill_with_objects()
instead of CollectedHeap::fill_with_object(). Note the extra
"s" in the method name. But MutableNUMASpace::ensure_parsability(),
where the change is needed, need to know about all the objects
that are allocated so I saw no better solution than to
implement my own loop. Any ideas on how I could re-use
fill_with_objects() instead are welcome.<br>
<br>
(2) CollectedHeap::_filler_array_max_size should be the
maximum size that can be covered by a fake Integer array. This
value is in words, but since the word size is different on
different platforms but the Integer size is always the same we
need to convert between word and sizeof(jint) at some point.
Unfortunately we do the conversion in the wrong direction,
which means that on 64 bit platforms we end up with a max size
that is 4 times larger than intended. This in turn makes us
overflow an int when we convert from a word size to the length
of the array that we are setting up.<br>
<br>
Here is the code that overflows:<br>
<br>
328 void<br>
329 CollectedHeap::fill_with_array(HeapWord* start, size_t
words, bool zap)<br>
330 {<br>
331 assert(words >= filler_array_min_size(), "too small
for an array");<br>
332 assert(words <= filler_array_max_size(), "too big
for a single object");<br>
333<br>
334 const size_t payload_size = words -
filler_array_hdr_size();<br>
335 const size_t len = payload_size * HeapWordSize /
sizeof(jint);<br>
336<br>
337 // Set the length first for concurrent GC.<br>
338 ((arrayOop)start)->set_length((int)len);<br>
339 post_allocation_setup_common(Universe::intArrayKlassObj(),
start, words);<br>
340 DEBUG_ONLY(zap_filler_array(start, words, zap);)<br>
341 }<br>
<br>
If filler_array_max_size() on line 332, which returns
CollectedHeap::_filler_array_max_size, has a too large value
we will overflow the int conversation on line 338.<br>
<br>
Testing:<br>
This fix solves the issue that was found in the reproducer
that I could set up on a Linux x64 machine. I have asked the
one who initially reported the issue to run on their Solaris
amd64 setup. I will also try to set up a reproducer on a
Solaris machine.<br>
<br>
I also ran the fix through JPRT. It did not fail, but there
are no NUMA tests in there as far as I know. But the change
for issue (2) was hopefully tested.<br>
<br>
Thanks,<br>
Bengt<br>
</blockquote>
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