<html xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=utf-8"><meta name=Generator content="Microsoft Word 15 (filtered medium)"><style><!--
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--></style></head><body lang=EN-US link=blue vlink="#954F72"><div class=WordSection1><p class=MsoNormal>“Stat calls in the import system were optimized in importlib a while back”</p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Yes, I’m aware of that, which is why I don’t have any specific suggestions off-hand. But given the differences in file systems between Windows and other OSs, it wouldn’t surprise me if there were a more optimal approach for NTFS to amortize calls better. Perhaps not, but it is still the most expensive part of startup that we have any ability to change, so it’s worth investigating.</p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Cheers,</p><p class=MsoNormal>Steve</p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Top-posted from my Windows phone</p><p class=MsoNormal><o:p> </o:p></p><div style='mso-element:para-border-div;border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal style='border:none;padding:0in'><b>From: </b><a href="mailto:brett@python.org">Brett Cannon</a><br><b>Sent: </b>Saturday, July 22, 2017 10:18<br><b>To: </b><a href="mailto:steve.dower@python.org">Steve Dower</a>; <a href="mailto:tritium-list@sdamon.com">Alex Walters</a><br><b>Cc: </b><a href="mailto:python-dev@python.org">Python-Dev</a><br><b>Subject: </b>Re: [Python-Dev] Python startup time</p></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal style='margin-bottom:12.0pt'><o:p> </o:p></p><div><div><p class=MsoNormal>On Sat, Jul 22, 2017, 07:22 Steve Dower, <<a href="mailto:steve.dower@python.org">steve.dower@python.org</a>> wrote:</p></div><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in'><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>I believe the trend is due to language like Python and Node.js, most of which aggressively discourage threading (more from the broader community than the core languages, but I see a lot of apps using these now), and also the higher reliability afforded by out-of-process tasks (that is, one crash doesn’t kill the entire app – e.g browser tabs).</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> </p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Optimizing startup time is incredibly valuable, and having tried it a few times I believe that the import system (in essence, stat calls) is the biggest culprit. The tens of ms prior to the first user import can’t really go anywhere.</p></div></div></blockquote></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Stat calls in the import system were optimized in importlib a while back to be cached in finders so at this point you will have to remove a stat call to lower that cost or cache more which goes into breaking abstractions or designing new APIs.</p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>-brett</p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in'><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> </p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Cheers,</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Steve</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> </p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Top-posted from my Windows phone</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> </p><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b>From: </b><a href="mailto:tritium-list@sdamon.com" target="_blank">Alex Walters</a><br><b>Sent: </b>Saturday, July 22, 2017 1:39<br><b>Cc: </b><a href="mailto:python-dev@python.org" target="_blank">'Python-Dev'</a></p></div></div></div><div><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><br><b>Subject: </b>Re: [Python-Dev] Python startup time</p></div></div></div><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> </p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> -----Original Message-----</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> From: Python-Dev [mailto:<a href="mailto:python-dev-bounces%2Btritium-" target="_blank">python-dev-bounces+tritium-</a></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> list=<a href="mailto:sdamon.com@python.org" target="_blank">sdamon.com@python.org</a>] On Behalf Of Paul Moore</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> Sent: Saturday, July 22, 2017 4:14 AM</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> To: David Mertz <<a href="mailto:mertz@gnosis.cx" target="_blank">mertz@gnosis.cx</a>></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> Cc: Barry Warsaw <<a href="mailto:barry@python.org" target="_blank">barry@python.org</a>>; Python-Dev <python-</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> <a href="mailto:dev@python.org" target="_blank">dev@python.org</a>></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> Subject: Re: [Python-Dev] Python startup time</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> </p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> </p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> It's a bit of a chicken and egg problem - Windows users avoid</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> excessive command line program invocation because startup time is</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> high, so no-one optimises startup time because Windows users don't use</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> short-lived command line programs. But I'm seeing a trend away from</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> that - more and more Windows tools these days seem to be comfortable</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> spawning subprocesses. I don't know what prompted that trend.</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> </p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>The programs I see that are comfortable spawning processes willy-nilly on</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>windows are mostly .net, which has a lot of the runtime assemblies cached by</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>the OS in the GAC - if you are spawning a second processes of yourself, or</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>something that uses the same libraries as you, the compile step on those can</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>be skipped. Unless you are talking about python/non-.NET programs, in which</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>case, I have no answer.</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> Paul</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> _______________________________________________</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> Python-Dev mailing list</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> <a href="mailto:Python-Dev@python.org" target="_blank">Python-Dev@python.org</a></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> <a href="https://mail.python.org/mailman/listinfo/python-dev" target="_blank">https://mail.python.org/mailman/listinfo/python-dev</a></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> Unsubscribe: <a href="https://mail.python.org/mailman/options/python-dev/tritium-" target="_blank">https://mail.python.org/mailman/options/python-dev/tritium-</a></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> list%<a href="http://40sdamon.com" target="_blank">40sdamon.com</a></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> </p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>_______________________________________________</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Python-Dev mailing list</p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><a href="mailto:Python-Dev@python.org" target="_blank">Python-Dev@python.org</a></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><a href="https://mail.python.org/mailman/listinfo/python-dev" target="_blank">https://mail.python.org/mailman/listinfo/python-dev</a></p></div></div><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Unsubscribe: <a href="https://mail.python.org/mailman/options/python-dev/steve.dower%40python.org" target="_blank">https://mail.python.org/mailman/options/python-dev/steve.dower%40python.org</a></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> </p></div></div></blockquote></div><p class=MsoNormal style='margin-left:4.8pt'>_______________________________________________<br>Python-Dev mailing list<br><a href="mailto:Python-Dev@python.org" target="_blank">Python-Dev@python.org</a><br><a href="https://mail.python.org/mailman/listinfo/python-dev" target="_blank">https://mail.python.org/mailman/listinfo/python-dev</a><br>Unsubscribe: <a href="https://mail.python.org/mailman/options/python-dev/brett%40python.org" target="_blank">https://mail.python.org/mailman/options/python-dev/brett%40python.org</a></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>