RE: [Xen-ia64-devel] Question about migration

[Kouya Shimura <kouya@xxxxxxxxxxxxxx>]

Hi,

In a SMP machine, complete synchronizing ITCs is impossible.
(i.e. each cpu's ITC has some error)
So small backward jump might occur in native SMP linux
except that a process is pinned to a cpu.
Does its DB perform pinning?

Thanks,
Kouya

Xu, Anthony writes:
> Isaku Yamahata wrote:
> > On Fri, Feb 01, 2008 at 03:08:24PM +0800, Xu, Anthony wrote:
> >> In DomU, ar.itc is not virtualized, so application can get itc
> >> directly. When DomU is migrated, how do you prevent vitc jump a lot(
> >> foreward/backward)?
> > 
> > Currently nothing prevents it. So a big itc jump can happen.
> > Anyway user application can be stopped/continued by SIGSTOP/SIGCONT
> > so that user application should be tolerable with such a big jump of
> > itc. 
> Foreward jump may be OK,
> How about back-ward jump? Application may be confused.
> 
> > 
> > So in theory it's ok. But I'm not sure in practical.
> > Do you have any concrete examples/scenario in your mind?
> No, But I know some DB use ITC,
> 
> Anthony
> 
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