Subj : Re: JOB: Sandbridge Technologies, White Plains, NY
To   : comp.programming.threads
From : Mayan Moudgill
Date : Fri Jul 15 2005 10:46 am

Joe Seigh wrote:
> Mayan Moudgill wrote:

> Realtime and good thread performance are somewhat antithetical.  FIFO
> locks perform less well than normal locks.  Lock-free is a better way
> to go.

We've already got some lock-free algorithms in place. The ISA uses 
load-word-reserved/store-word-conditional as our "synchronization" 
primitives, so we can implement stuff like atomic increment, lock-free 
LIFOs etc.

   Plus most of the conventional solutions I've see for priority
> inversion are really suboptimal.
   Basically you get all your RT guarantees
> by crippling everything so lower priority threads can't perform better
> than high priority threads.

Our biggest issue is the difference between "pinned" and "unpinned" 
threads. A pinned thread is one which is locked down to a hardware 
thread, and will not get switched. For perfomance, you want to use 
spin-based synchronization mechanisms as opposed to 
dequeing/context-switching when a pinned thread needs to wait.


> And try to avoid preemptive signaling like Linux NPTL does.  Unless 
> Posix mandates
> it as a scheduling point. 

kill and signalling have all kinds of ugliness associated with it. We 
don't have a notion of a process (though we were thinking of 
thread-groups) so we avoid the real ugliness, but even pthread_kill is 
pretty ugly.

.