Messages in this thread | | | Date | Tue, 11 Mar 2003 07:40:15 -0500 (EST) | From | "Richard B. Johnson" <> | Subject | Re: is irq smp affinity good for anything? |
| |
On Tue, 11 Mar 2003 uaca@alumni.uv.es wrote:
> > > if IRQ affinity cannot help in interrupt latency and > interrupt auto/balancing get's the same throughtput > as irq binding... what is irq smp affinity for??? > > from this mail from intel > http://www.uwsg.iu.edu/hypermail/linux/kernel/0301.0/1886.html > I understand that intel's interrupt auto/balancing works equal that manually > tunning the interrupts.... > > so? > > Ulisses > > > > On Mon, Mar 10, 2003 at 11:22:22PM +0100, uaca@alumni.uv.es wrote: > > > > Hi all > > > > I have measured interrupt latency of a bi-processor system with akpm's intlat/timepeg > > utilities and kernel 2.4.20. The system uses is a two-way PIII@800Mhz > > -- Intel motherboard, ISP 2100 if I remember ok, with a SCSI disk on a aic-7896 > > > > I tried to know if I could reduce the latency of an interrupt handler by > > binding this handler to a particular cpu and not allowing any other > > interrupt to execute in that cpu. > > > > I found that overall latency increases, but also the latency on both cpus, > > that is, I could not reduce the latency on the interrupt I was interested > > > > I also tried to disallowing just scsi & ethernet handlers to execute on the > > cpu in wich I'm binding the interrupt handler I'm insterested with, I get > > similar results > > > > the interrupt handler I'm interested with is an ATM card receiving > > around 6000 interrupts/second > > [SNIPPED...]
33 MHz machines easily handle 6,000 interrupts per second -- unless you are trying to execute code within that interrupt that requires 1/6000th of a second to execute! Perhaps it's not a "latency" problem, but an interrupt code-bloat problem where most of the stuff should be executed out of the interrupt context.
There are timer queues and kernel threads available that might help you. Also a tightly-coupled user-mode daemon that uses your driver only to interface with the hardware and not do any "logic" is probably the way to go.
Cheers, Dick Johnson Penguin : Linux version 2.4.20 on an i686 machine (797.90 BogoMips). Why is the government concerned about the lunatic fringe? Think about it.
- 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/
| |