[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] [PATCH] Adjust time init sequence
>From: Keir Fraser [mailto:keir.fraser@xxxxxxxxxxxxx] >Sent: Thursday, December 11, 2008 8:45 AM > >On 11/12/2008 00:23, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote: > >>> Is it really safe to use NOW() before init_percpu_time()? >Seems dodgy. >> >> Where did you mean by using NOW before init_percpu_time? >> I moved do_settime earlier but with a zero system stamp now >> which matches the line behind to init stime_platform_time to zero. >> To me there's no difference to initialize wallclock at zero point >> or sometime after with a NOW() drift, which should cause similar >> result to wc_sec/wc_nsec. > >init_platform_time() -> plt_overflow() -> NOW() > >Perhaps the above is safe though? Will NOW() return zero for an >uninitialised per-cpu time sstructure (since stime_local_stamp >and tsc_scale >are both zero)? > I guess not, due to same reason as why I sent out 1st patch idle vcpu state entry. The point is the current TSC value, which count from power on and is translated to a dozens of seconds for elapsed time upon a zero tsc stamp. :-( I didn't realize that point in the start... Thanks, Kevin _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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