Re: [Xen-devel] [timer/ticks related] dom0 hang during boot on large 1TB system

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> Keir Fraser <keir.fraser@xxxxxxxxxxxxx> 22.12.09 14:35 >>>
>On 22/12/2009 11:10, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:
>
>> Nevertheless I remain convinced that the problem ought not to be fixed
>> by a kernel change (and even less by one that modifies Xen-unspecific
>> code). Any patch to this effect, unless I should be convinced otherwise,
>> has my explicit up front NAK (in case this counts anything).
>
>Well, I must say the kernel patch looked quite sensible to me. If no other
>reason than reinforcing the fact that jiffy values should always be compared
>using the provided macros. But I'm happy to have a hypervisor patch as well,
>if we can work out what it should be. I'm still unclear on the reason why
>slow page scrubbing causes this problem - Oracle's explanation hasn't
>convinced me yet.

There's another thing that seems inconsistent with this report: jiffies
itself as well as all the arithmetic in calibrate_delay_direct() is using
"unsigned long", so is being done 64-bit on x86-64 (which we're
talking about here). Hence I can see even less how an overflow could
have happened, or how using explicit 64-bit types (or get_jiffies_64())
here can help.

Jan


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