Wikimedia Bugzilla is closed!

From support desk: https://www.mediawiki.org/wiki/Thread:Project:Support_desk/Caching_issue_makes_MediaWiki_painfully_slow/reply_(4)

This was caused by mw bug (or bug in some xcache version).

xcache_get returns NULL if nothing can be acquired from cache, but mw waits for false.

if ( $this->get( $key ) === false ) {

at line 147 of includes/objectcache/BagOStuff.php, while xcache will return NULL in this case, so

for ( $i = 0; $i < MSG_WAIT_TIMEOUT && !$this->mMemc->add( $lockKey, 1, MSG_LOCK_TIMEOUT ); $i++ ) {

at line 581 of includes/cache/MessageCache.php will get timeout in 10 seconds (default value).

mediawiki 1.20.2, xcache v3.0.1

I'll report this to bugzilla if not forget.