Subj : Re: Lock Free -- where to start
To   : comp.programming.threads
From : David Schwartz
Date : Thu Sep 29 2005 12:30 pm


"Joe Seigh" <jseigh_01@xemaps.com> wrote in message 
news:AridnXxvsKImsKHeRVn-qQ@comcast.com...

> Depends on how many processors you have.  There may be other things 
> causing
> context switching also but blocking on a lock certainly isn't going to 
> help
> performance.

    No, that's not true. Blocking on a lock is going to help performance 
because useful work will be done until it's possible for the blocked thread 
to run without contention. Blocking on a lock is good because it allows 
contention to be avoided.

    Lock free algorithms only help if the thing contended for is so critical 
and important that you can't do much of anything else (on the entire system) 
without accessing it. That's why they're very useful inside kernels where 
this is often true and almost useless in application where it almost never 
is.

    DS

.