On Thursday, February 09, 2012 01:58:53 PM Kirk Wallace did opine: > On Thu, 2012-02-09 at 12:39 -0500, gene heskett wrote: > > On Thursday, February 09, 2012 12:38:04 PM Ben Jackson did opine: > > > On Thu, Feb 09, 2012 at 11:23:47AM +0200, andy pugh wrote: > > > > It is servo-thread only as it uses floating-point. I am not > > > > entirely sure why. > > > > > > Aha, that's why I added the laser-thread in my HAL: A base-period > > > thread with FP allowed. On a modern CPU it's no big deal. > > > > I wonder if that is a hangover from when most computers needed a > > floating point chip installed? > > > > Cheers, Gene > > My understanding is, it is because RTAI (loadrt) has no floating point > functions. Floating point has to be done in userland (loadusr). But now > that I mention it, then why would one specify even a servo thread? I > guess I don't have an understanding.
I'd be the first to admit mine is pretty hazy too. But with regard to the context switch it took when the FP chip was a separate chip, I venture a guess that since the FP stuff is today essentially just more registers in the chip to load and unload, the hit from that switch in today's cpu's might be less that say 50 machine cycles, and even less in a multi-threaded setup that can go on, waiting for the FPO results by doing something else by leaving the hyper-threading on in the bios. However, this hyper- threading AIUI is nothing but a hard coded context switch, and we shut that off precisely because the context switch is a relatively large slice of time during which IRQ's are locked out. This atom board is the first board I've ever had with hyper-threading, and my personal opinion is that its nothing but a marketing gizmo for the unwashed masses who see cpu info claiming 4 core on a 2 core cpu, and that even the gamers trying to get every cycle they can, would probably be better off with it disabled. My $0.02 in 1934 dollars, adjust for inflation. ;-) Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> Q: How many marketing people does it take to change a light bulb? A: I'll have to get back to you on that. ------------------------------------------------------------------------------ Virtualization & Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
