Messages in this thread | | | Subject | Re: [RFC] must fix lists | From | Albert Cahalan <> | Date | 23 Oct 2003 21:06:57 -0400 |
| |
On Thu, 2003-10-23 at 19:46, Nick Piggin wrote:
> +o alan, Albert Cahalan: 1000 HZ timer increases the need for a stable time > + source. Many laptops, SMI can lose ticks. ACPI timers? TSC?
Oh, I have an example for you.
Consider the Intel Plumas chipset. There are some predictable time windows during which the RTC will return garbage. The BIOS "fix" leads to SMI/SMM stuff stealing large chunks of CPU time. On a logic analyser, somebody at work observed chunks of time as large as 4 ms. That's 3 to 5 clock ticks. Maybe that isn't worst-case even.
To avoid this disaster, Linux must _never_ touch the RTC registers. The HPET can be used instead. The TSC is of course also reliable, but Linux stops using it as soon as a problem hits!
The ignore-the-TSC code really should be doing just the opposite. Ticks are likely to be lost. I've never seen an unstable TSC. :-)
> o 64-bit dev_t. Seems almost ready, but it's not really known how much > work is still to do. Patches exist in -mm but with the recent rise of the > neo-viro I'm not sure where things are at.
Hey, 32-bit dev_t is in already. That's it. Done.
- 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/
| |