Messages in this thread | | | Date | Wed, 09 Oct 2002 17:50:30 -0700 | From | Dan Kegel <> | Subject | Re: [PATCH 2/3] High-res-timers part 2 (x86 platform code) take 5.1 |
| |
george anzinger wrote: > Linus Torvalds wrote: > > I really don't get the notion of partial ticks, and quite frankly, this > > isn't going into my tree until some major distribution kicks me in the > > head and explains to me why the hell we have partial ticks instead of just > > making the ticks shorter. > ... > > Making ticks shorter causes extra overhead ALL the time, > even when it is not needed. Higher resolution is not free > in any case, but it is much closer to free with this patch > than by increasing HZ (which, of course, can still be > done). Overhead wise and resolution wise, for timers, we > would be better off with a 1/HZ tick and the "on demand" > high-res interrupts this patch introduces.
Seems reasonable to me. Increasing HZ adds overhead - it makes sense to incur the interrupt overhead only when it's needed. In my case, we want to provide fairly precise network delays (we're doing a WAN simulator), and still hit line rate. Now, I'm way far from the code, but I suspect that the interrupt overhead needed to get the precision the customer is calling for would be totally prohibitive. I dunno if we'll get the precision the customer wants with George's approach, but we'll get a lot closer than we would setting HZ to 10000 on our wimpy little embedded platform.
George's approach would work a lot better when doing lots of UML VM's on a single box, too, wouldn't it? - Dan - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |