update slows down materially on some change within here.
"./test perf", random-upserts-inc result.

SLOWER HERE:
commit 85a009c44a64bc47b471fb95508a60659a1a01f5
Author: Eliot Horowitz <eliot@10gen.com>
Date: Wed Jun 15 18:02:15 2011 -0400
fix for 32bit

commit d194a8bccae8b1860915dbbf21ec2dad1867ab87
Author: Eliot Horowitz <eliot@10gen.com>
Date: Wed Jun 15 17:53:38 2011 -0400

cleaning

commit 07695200a1c0e2fbb1b4c2462eb263e639a2db31
Author: Eliot Horowitz <eliot@10gen.com>
Date: Wed Jun 15 17:46:25 2011 -0400

add db/record.cpp

commit 9ce1c143b4ee27782123224fe6ddf1a4be13849e
Author: Eliot Horowitz <eliot@10gen.com>
Date: Wed Jun 15 17:45:57 2011 -0400

some cleaning

commit 037cf2ea57f27e11a28cf54f3b6bf98944230f93
Author: Eliot Horowitz <eliot@10gen.com>
Date: Wed Jun 15 17:29:18 2011 -0400

yield with disk prep for ClientCursor SERVER-2563

commit 5a5a18228173a9bb8b345f5695e8126e6d288312
Author: Eliot Horowitz <eliot@10gen.com>
Date: Wed Jun 15 17:28:52 2011 -0400

yielding with disk lock backend, hooked into updates by _id

commit 06ed5bd1986e8bfc7f49401ddb464f8afd8b4e3b
Author: Eliot Horowitz <eliot@10gen.com>
Date: Wed Jun 15 16:48:12 2011 -0400

make static

commit 1d19f0498ccdb0478ae0b5bf350080c9e82f0b74
Author: dannenberg <dannenberg.matt@gmail.com>
Date: Wed Jun 15 16:37:23 2011 -0400

fixed white space mistake

commit a65dd3a524feabcd4449412d803197dd9559e7db
Author: dannenberg <dannenberg.matt@gmail.com>
Date: Wed Jun 15 16:32:58 2011 -0400

prompt can be string or function and works with spidermonkey

commit 2fdf334c6b9526e6997a7812c09371921867ddf1
Author: dannenberg <dannenberg.matt@gmail.com>
Date: Wed Jun 15 14:51:52 2011 -0400

fixed custom prompt in spidermonkey

FASTER HERE:
"git" : "1c180c6a60126e8468e71d7b36b29ee0d7b7bdb9"
Date: Wed Jun 15 11:35:46 2011 -0400
SERVER-3267 very basic custom prompt added