perf on a random app server showed >1.4% of all cycles being spent in array_change_key_case() in AutoLoader.php#59. This code is only hit if $wgAutoloadAttemptLowercase is true. Is it still needed?
Capturing messages on the autoloader debug log channel could help determining that. If it's not needed, setting this config var to false would be a easy modest performance win.
Since this code is hot, I assume AutoLoader.php runs before the Composer autoloader, and that the case manipulation happens for every class that lives in an external depedency. If that is true, then it might be good idea to relegate the code that does the case manipulation to a discrete legacy autoloader that runs last.
Change 356841 had a related patch set uploaded (by Krinkle; owner: Ori Livneh):
[operations/mediawiki-config@master] Capture messages on 'autoloader' debug log channel
We run the MediaWiki autoloader before composer because at that time most classes were still in MediaWiki's autoloader - we should check that it's still the case. IIRC there are PHP4 serialized objects in the database somewhere that depend upon being able to autoload with the lowercase class name.
Change 356841 merged by jenkins-bot:
[operations/mediawiki-config@master] Capture messages on 'autoloader' debug log channel
Log entries show for:
Class Mediawiki\Widget\DateInputWidget was loaded using incorrect case 34,321 Class SpecialRecentchanges was loaded using incorrect case 7,867 Class SpecialRecentchangeslinked was loaded using incorrect case 6,618 Class historyblobcurstub was loaded using incorrect case 3,249 Class xml was loaded using incorrect case 26 Class concatenatedgziphistoryblob was loaded using incorrect case 14 Class historyblobstub was loaded using incorrect case 7
Class SpecialRecentchanges was loaded using incorrect case 7,867
Class SpecialRecentchangeslinked was loaded using incorrect case 6,618
https://gerrit.wikimedia.org/r/361096
All the other ones (except xml?) look like they're serialized stuff from the PHP4 era.
history blobs are tricky since they are probably serialized in the older read-only DBs that we don't normally mess around with (some are just clones with no replication AFAIK).
If we have a small list of classes that we know that could be serialized, could we just add their lowercase variants to the autoload classmap?
$ head -n1 autoloader.log && tail -n1 autoloader.log 2017-10-12 07:41:03 .. 2017-10-12 22:05:42 .. $ cat autoloader.log | cut -d' ' -f9- | sort | uniq -c 1379 Class concatenatedgziphistoryblob was loaded using incorrect case 33433 Class historyblobcurstub was loaded using incorrect case 247 Class historyblobstub was loaded using incorrect case 26 Class HtmlForm was loaded using incorrect case 82 Class HTML was loaded using incorrect case 5 Class HTTP was loaded using incorrect case 361 Class Mediawiki\Widget\SelectWithInputWidget was loaded using incorrect case 97 Class XML was loaded using incorrect case
Change 384288 had a related patch set uploaded (by Ori.livneh; owner: Ori Livneh):
[mediawiki/core@master] Add lowercase variants to the autoloader for legacy history blob classes
Change 384303 had a related patch set uploaded (by Ori.livneh; owner: Ori Livneh):
[mediawiki/extensions/Wikibase@master] Fix letter-case of XML
Change 384308 had a related patch set uploaded (by Ori.livneh; owner: Ori Livneh):
[mediawiki/extensions/PageAssessments@master] Fix class name letter-case
Change 384309 had a related patch set uploaded (by Ori.livneh; owner: Ori Livneh):
[mediawiki/extensions/UploadWizard@master] Fix letter-case of class name
Change 384310 had a related patch set uploaded (by Ori.livneh; owner: Ori Livneh):
[mediawiki/extensions/MassMessage@master] Fix letter-case of class name
Change 384308 merged by jenkins-bot:
[mediawiki/extensions/PageAssessments@master] Fix class name letter-case
Change 384309 merged by jenkins-bot:
[mediawiki/extensions/UploadWizard@master] Fix letter-case of class name
Change 384310 merged by jenkins-bot:
[mediawiki/extensions/MassMessage@master] Fix letter-case of class name
Change 384303 merged by jenkins-bot:
[mediawiki/extensions/Wikibase@master] Fix letter-case of XML
Change 384288 merged by jenkins-bot:
[mediawiki/core@master] Add lowercase variants to the autoloader for legacy history blob classes
Change 385405 had a related patch set uploaded (by Krinkle; owner: Ori Livneh):
[integration/jenkins@master] Add $wgAutoloadAttemptLowercase = false to dev settings
Change 385405 merged by jenkins-bot:
[integration/jenkins@master] Add $wgAutoloadAttemptLowercase = false to dev settings
Change 385978 had a related patch set uploaded (by Ori.livneh; owner: Ori Livneh):
[operations/mediawiki-config@master] labs: Set $wgAutoloadAttemptLowercase to false
Change 385978 merged by jenkins-bot:
[operations/mediawiki-config@master] labs: Set $wgAutoloadAttemptLowercase to false
There is only a single entry in autoloader.log for the past three days:
2017-10-23 13:11:02 [We3qZgpAEDQAAJt3Qz0AAABF] mw1287 wikidatawiki 1.31.0-wmf.4 autoloader INFO: Class HTTP was loaded using incorrect case
I can't find the culprit code, but it is not possible to grep for certain patterns (e.g. $cls = 'HTTP'; $req = new $cls;).
$wgAutoloadAttemptLowercase is currently set to false for Jenkins tests, MediaWiki-Vagrant, and Labs.
Change 386384 had a related patch set uploaded (by Ori.livneh; owner: Ori Livneh):
[operations/mediawiki-config@master] Set $wgAutoloadAttemptLowercase to false
Change 386384 merged by jenkins-bot:
[operations/mediawiki-config@master] Set $wgAutoloadAttemptLowercase to false
Mentioned in SAL (#wikimedia-operations) [2017-10-25T14:47:09Z] <mattflaschen@tin> Synchronized wmf-config/InitialiseSettings.php: T166759: Set $wgAutoloadAttemptLowercase to false (duration: 00m 50s)
Change 387971 abandoned by Krinkle:
Re-enable $wgAutoloadAttemptLowercase for older branches
Change 398453 had a related patch set uploaded (by Mainframe98; owner: Mainframe98):
[mediawiki/core@master] Fix additional usage of incorrect case
Change 398453 merged by jenkins-bot:
[mediawiki/core@master] Fix additional usage of incorrect case
Change 415759 had a related patch set uploaded (by MaxSem; owner: MaxSem):
[operations/mediawiki-config@master] beta: remove $wgAutoloadAttemptLowercase
Change 415759 merged by jenkins-bot:
[operations/mediawiki-config@master] beta: remove $wgAutoloadAttemptLowercase