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<p style="margin: 0px 0px 1.2em !important;">Hi Brian,<br>
I have been playing some more with the benchmark you provided
here:</p>
<p style="margin: 0px 0px 1.2em !important;"><a href="https://gist.github.com/broneill/3a39051635e3cb758d0cca5a963c685e" class="moz-txt-link-freetext">https://gist.github.com/broneill/3a39051635e3cb758d0cca5a963c685e</a></p>
<p style="margin: 0px 0px 1.2em !important;">The following patch
seems to help quite significantly:</p>
<p style="margin: 0px 0px 1.2em !important;"><a href="https://cr.openjdk.org/~mcimadamore/panama/segment_normalize_offsets.patch" class="moz-txt-link-freetext">https://cr.openjdk.org/~mcimadamore/panama/segment_normalize_offsets.patch</a></p>
<p style="margin: 0px 0px 1.2em !important;">Here are the
benchmark results:</p>
<p style="margin: 0px 0px 1.2em !important;">(before)</p>
<pre style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;font-size: 1em; line-height: 1.2em;margin: 1.2em 0px;"><code style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;margin: 0px 0.15em; padding: 0px 0.3em; white-space: pre-wrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-radius: 3px; display: inline;white-space: pre; overflow: auto; border-radius: 3px; border: 1px solid rgb(204, 204, 204); padding: 0.5em 0.7em; display: block !important;">Benchmark Mode Cnt Score Error Units
BinarySearch.binarySearch_panama avgt 30 61.404 ? 1.315 ns/op
BinarySearch.binarySearch_unsafe avgt 30 28.099 ? 0.330 ns/op
</code></pre>
<p style="margin: 0px 0px 1.2em !important;">(after)</p>
<pre style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;font-size: 1em; line-height: 1.2em;margin: 1.2em 0px;"><code style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;margin: 0px 0.15em; padding: 0px 0.3em; white-space: pre-wrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-radius: 3px; display: inline;white-space: pre; overflow: auto; border-radius: 3px; border: 1px solid rgb(204, 204, 204); padding: 0.5em 0.7em; display: block !important;">Benchmark Mode Cnt Score Error Units
BinarySearch.binarySearch_panama avgt 30 38.103 ? 0.471 ns/op
BinarySearch.binarySearch_unsafe avgt 30 27.556 ? 0.208 ns/op
</code></pre>
<p style="margin: 0px 0px 1.2em !important;">We believe there must
be some C2 issue lurking in there - basically we’re forcing all
offsets to be positive using this:</p>
<pre style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;font-size: 1em; line-height: 1.2em;margin: 1.2em 0px;"><code style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;margin: 0px 0.15em; padding: 0px 0.3em; white-space: pre-wrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-radius: 3px; display: inline;white-space: pre; overflow: auto; border-radius: 3px; border: 1px solid rgb(204, 204, 204); padding: 0.5em 0.7em; display: block !important;">@ForceInline
private static long normalize(long offset) {
if (offset < 0) {
throw new IndexOutOfBoundsException("Offset is < 0");
}
return offset & Long.MAX_VALUE;
}
</code></pre>
<p style="margin: 0px 0px 1.2em !important;">Now, surprisingly, if
the “& Long.MAX_VALUE” is dropped, performance dips again. I
believe we lose track of the positivity here and the above patch
provides some kind of workaround.</p>
<p style="margin: 0px 0px 1.2em !important;">I’d be interested to
know if this patch helps the situation with your bigger
benchmark, or if things stay the same (in which case, we would
have to conclude that this benchmark, while interesting, is
perhaps not reflective of the issues in your bigger codebase).</p>
<p style="margin: 0px 0px 1.2em !important;">Thanks<br>
Maurizio</p>
<p style="margin: 0px 0px 1.2em !important;">On 06/07/2023 23:19,
Brian S O’Neill wrote:</p>
<p style="margin: 0px 0px 1.2em !important;"></p>
<div class="markdown-here-exclude">
<p></p>
<blockquote type="cite" cite="mid:b456f83b-9d4e-01bc-90cc-63749f9218b3@gmail.com">When
I use the "ALL" MemorySegment instead of allocating
MemorySegments on the fly for copies, the performance
regression drops to ~2%.</blockquote>
<p></p>
</div>
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