Re: kvm very slow

Luca
2007-08-07T12:08:08Z

On 8/7/07, Dor Laor <dor.laor-atKUWr5tajBWk0Htik3J/w@public.gmane.org> wrote:
> Luca claims the HPET intefer the RTC. Can it be disabled? ( I know some
> new chipsets implement rtc using HPET).

Basically HPET can operate in legacy mode - where it uses the same IRQ
as the RTC (and RTC won't deliver any interrupt) - or in "standard"
mode where the IO-APIC can be configured to deliver the interrupt on
any line. ATM Linux can only use the legacy mode.
You can of course disable HPET, but then it won't be available for
in-kernel timekeeping (in case e.g. the TSC is not stable/synced). I'd
rather add support for HPET as timer in QEMU...
On the original issue: if the host is running at HZ=100 then the
precision of the timer may be a awkward (usually around 20ms), but
it's surprising that it causes such a huge drift.

Luca