Messages in this thread | | | Date | Wed, 15 Dec 2004 17:35:41 +0100 | From | Ingo Molnar <> | Subject | Re: [patch, 2.6.10-rc3] safe_hlt() & NMIs |
| |
* Linus Torvalds <torvalds@osdl.org> wrote:
> > > On Wed, 15 Dec 2004, Ingo Molnar wrote: > > > > i ran the stresstest overnight with the 10 KHz NMI, and not a single > > time did the new branch trigger, out of hundreds of millions of IRQs and > > NMIs. I think this suggests that the race doesnt exist in current CPUs. > > That may well be true, but I'm not convinced your test is meaningful > or shows anything. > > The thing is, either the CPU is busy, or it's idle. If it's busy, > you'll never see this. And if it's idle, it will always be _in_ the > "halt" instruction.
i deliberately started a test where there was roughly 50% idle time.
> The only way to see the case is in the borderline cases, and if/when > there are multiple different interrupts (first non-NMI interrupt takes > it out of the hlt, and then the NMI happens to catch the sti). And > quite frankly, I don't see how you would stress-test it. A 1kHz timer > interrupt with a 10kHz NMI interrupt is still very infrequent > interrupts...
i started an infinite loop that generated disk IRQs, and started a network test that generated network IRQs. The IRQ rate was roughly 10K/sec - this combined with the 10K/sec NMI rate should be an adequate mix. (I also made sure that it's really default_idle that is used.)
Ingo - 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/
| |