In most cases they are utterly unable to answer that question honestly.
A comment http://lwn.net/Articles/447204/ at LWN.net in 2011.
Ingo Molnar quotes
Ingo Molnar
Ingo Molnár, employed by Red Hat as of May 2013, is a Hungarian Linux hacker. He is best known for his contributions to the operating system in terms of security and performance. Wikipedia
Quotes Ingo Molnar
A comment http://lwn.net/Articles/447204/ at LWN.net in 2011.
From a message http://www.ussg.iu.edu/hypermail/linux/kernel/9906.0/0746.html to the Linux Kernel mailing list in 1999.