Anomalous performance increase from mutex profiling

[Surer Dink]

On 4/17/06, Kris Kennaway <kris at obsecurity.org> wrote:
> On Mon, Apr 17, 2006 at 03:54:07AM -0400, Surer Dink wrote:
> > Please excuse if this is a stupid question - but might using MCS or
> > QOLB locks in this situation be useful?
>
> What are they?

Mellor-Crummy Scott:
http://www.cs.rochester.edu/u/scott/papers/1991_ASPLOS_sync.pdf

An overview comparing various possible optimizations for a few lock
types, including MCS and QOLB:
ftp://ftp.cs.utexas.edu/pub/dburger/papers/ISCA97_qolb.pdf

I believe the QOLB proposal only suggested hardware modificaition for
performance improvement, but could be implemented entirely in software
- the overheads are high, but offer substantial performance benefit in
high contention situations.  MCS is based on QOSB, however fully
implemented in software.

There is also a proposal for changing lock to MCS dynamically, however
I have not read it:
ftp://ftp.cag.lcs.mit.edu/pub/papers/pdf/reactive.pdf