<div dir="ltr"><div class="gmail_default" style="font-family:trebuchet ms,sans-serif"><div class="gmail_default">(Sorry if you receive this email twice, I sent it from another account and it seems like it didn't reach the mailing list then)</div><div class="gmail_default"><br></div><div class="gmail_default">Hi erlangers,</div><div class="gmail_default"><br></div><div class="gmail_default">Yeah! It's me talking about performance, you read that subject right 🤦♂️</div><div class="gmail_default">Anyway… At NextRoll we're in the process of migrating our systems from OTP21 to OTP22 (not 23, yet) and our tests showed a <b>huge</b> impact on performance in general, that was not associated to anything in particular.</div><div class="gmail_default"><br></div><div class="gmail_default">While trying to figure out what was causing it, we came up with a very very basic example of things that are consistently slower in OTP22.</div><div class="gmail_default"><br></div><div class="gmail_default">I created this gist to show it: <a href="https://gist.github.com/elbrujohalcon/d4e995fbc4b93fadddfd1f0d6b9f8121" target="_blank" style="font-family:Arial,Helvetica,sans-serif">https://gist.github.com/elbrujohalcon/d4e995fbc4b93fadddfd1f0d6b9f8121</a></div><div class="gmail_default"><br></div><div class="gmail_default">I'm aware that these kinds of micro-benchmarks are treacherous and they may vary wildly depending on context. Nevertheless, on both on one of our servers in AWS and on my machine (A MacOS Pro running Catalina 10.15.5) and using kerl to install multiple versions of OTP 21 and 22… every single time I run the tests I found the same results…</div><div class="gmail_default"><br></div><div class="gmail_default">Always starting the nodes with <i>erl -boot start_clean </i>then running the following in both OTP21 and OTP22…</div><div class="gmail_default" style="font-family:Arial,Helvetica,sans-serif"><font face="monospace"><br></font></div><div class="gmail_default" style="font-family:Arial,Helvetica,sans-serif"><font face="monospace">c(test), test:bench({test, lrec}, 250, 5000, 2000).</font><br></div><div class="gmail_default"><br></div><div class="gmail_default">…generates very similar numbers in both versions, regardless of the numbers used for the different parameters. But…</div><div class="gmail_default" style="font-family:Arial,Helvetica,sans-serif"><font face="monospace"><br></font></div><div class="gmail_default" style="font-family:Arial,Helvetica,sans-serif"><font face="monospace">c(test), test:bench({test, rec}, 250, 5000, 2000).</font><br></div><div class="gmail_default"><br></div><div class="gmail_default">…consistently generates larger results in OTP22 than OTP21. I tried with different values for the number of tests, the number of lists and their length and sometimes the difference is more evident, sometimes less… but OTP22 times are <b>always</b> larger.</div><div class="gmail_default"><br></div><div class="gmail_default">I found this in the OTP22 readme…</div><div class="gmail_default"><br></div><div class="gmail_default" style="font-family:Arial,Helvetica,sans-serif"><font face="monospace"> OTP-15427 Application(s): erts<br> Appending lists (The ++ operator) will now yield<br> properly on large inputs.</font><br></div><div class="gmail_default"><br></div><div class="gmail_default">So… questions…</div><div class="gmail_default">1. Has anybody experienced (and hopefully solved) this problem before when migrating to OTP22?</div><div class="gmail_default">2. Do you think OTP-15427 can be related to what I'm seeing?</div><div class="gmail_default">3. Can someone confirm if you also experience the same difference in performance when running the same benchmarks that I pasted on that gist?</div><div class="gmail_default">4. Is there anything else I should try/test/use to check?</div><div class="gmail_default">5. Am I going slightly mad?</div><div class="gmail_default"><br></div><div class="gmail_default">Thanks in advance, cheers :)</div><font color="#888888" style="font-family:Arial,Helvetica,sans-serif"><br class="gmail-Apple-interchange-newline"></font></div><div><br></div>-- <br><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><table border="0" cellpadding="0" cellspacing="0">
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