AFAIK, BKL is no more useful.
p.s.
http://www.internetnews.com/skerner/2010/11/linux-2637-kills-the-big-kerne.html 

so, you can ignore it.

However, if you are interested to know its details, go thro' http://lwn.net/Articles/86859/


Date: Thu, 29 Dec 2011 14:33:42 +0530
From: sandeep kumar <coolsandyforyou@gmail.com>
Subject: What is Big Kernel Lock?
To: kernelnewbies@kernelnewbies.org
Message-ID:
    <CAL7WMDdSFA37iOgqo8LC+JLM05uMK-VhNkxPdUqDiCjKCypdiQ@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"

Hi All,
Can any one tell me the significance of BKL?

--
With regards,
Sandeep Kumar Anantapalli,
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