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<p class="MsoNormal"> Apologies, human error – here’s the message I intended:<br>
<br>
Thank you! I’ve updated the PR accordingly and summarized the benchmarks in the description. Here’s the short version:<o:p></o:p></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1">For small payloads, unsynchronized and optimized versions are 2-4x faster than base<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1">For large payloads, optimized version is 3x faster than base or unsynchronized<o:p></o:p></li></ul>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> I discovered a capacity-related incompatibility between ByteArrayOutputStream and MemoryOutputStream: the size() method returns int, but MemoryOutputStream can exceed that value. I added range checking to size() and a new sizeAsLong()
method… but it really makes me wonder MemoryOutputStream belongs as a subclass of ByteArrayOutputStream. It now has two significant incompatibilities: ignoring the protected fields, and size restrictions.<o:p></o:p></p>
<p class="MsoNormal"> John<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>From:</b> Engebretson, John <br>
<b>Sent:</b> Wednesday, April 2, 2025 12:58 PM<br>
<b>To:</b> 'Alan Bateman' <alan.bateman@oracle.com>; Markus KARG <markus@headcrashing.eu>; core-libs-dev@openjdk.org<br>
<b>Subject:</b> RE: [EXTERNAL] JDK-8352891 Performance improvements to ByteArrayOutputStream<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> Thank you! I’ve updated the PR accordingly and summarized the benchmarks in the description. Here’s the short version:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>From:</b> Alan Bateman <<a href="mailto:alan.bateman@oracle.com">alan.bateman@oracle.com</a>>
<br>
<b>Sent:</b> Wednesday, April 2, 2025 5:52 AM<br>
<b>To:</b> Engebretson, John <<a href="mailto:jengebr@amazon.com">jengebr@amazon.com</a>>; Markus KARG <<a href="mailto:markus@headcrashing.eu">markus@headcrashing.eu</a>>;
<a href="mailto:core-libs-dev@openjdk.org">core-libs-dev@openjdk.org</a><br>
<b>Subject:</b> RE: [EXTERNAL] JDK-8352891 Performance improvements to ByteArrayOutputStream<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p><strong><span style="font-family:"Calibri",sans-serif;background:#FFFF99">CAUTION</span></strong><span style="background:#FFFF99">: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the
sender and know the content is safe.</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">On 31/03/2025 16:51, Engebretson, John wrote:<o:p></o:p></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal"> Alan – is this what you have in mind:<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">ByteArrayOutputStream.getInstance() // returns existing class<o:p></o:p></p>
<p class="MsoNormal">ByteArrayOutputStream.getUnsynchronizedInstance() // returns subclass of BAOS that overrides the synchronization<o:p></o:p></p>
<p class="MsoNormal">ByteArrayOutputStream.get<Scalable|Memory|Fast|Segmented>Instance() // returns the new class<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
</blockquote>
<p class="MsoNormal" style="margin-bottom:12.0pt"><br>
BAOS has been synchronized since JDK 1.0. While undocumented, it's possible that existing code depends on this 30 year behavior so I think we are stuck with it.<br>
<br>
The removal of biased locking has spurred on a few complaints that the class is needlessly synchronized. A static factory to return an unsynchronized BOAS would help but only if it isn't used with code that assumes all operations are synchronized. So I think
we will have to look at the API docs for this.<br>
<br>
It's not clear that we need to have several implementation with different performance tradeoffs. So I think part of the exploration will be to see what usages perform better or worse, and whether having a parameter to specify the initial size or some hint of
the max size would help the discussion.<br>
<br>
-Alan<o:p></o:p></p>
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