Hello Eddie, Am Montag 15 Oktober 2007 06:13:44 schrieb Dong, Eddie: > >That 0.1% kills me though. do you mean, that every 1 second, 1 > >will be 1ms > >off? And for every second thereafter, leaving me with 1 second > >drift after > >only 1000 seconds? > > Oh, that is not my intension :-( > I just put a rought estimation here. In old Xen > time, I know there are ~10-30 seconds shift after ~10 hours.
That's about the same, isn't it? That's 30 seconds shift after 36000 seconds and really a lot. > >I am looking for an absolute value for time difference between > >guest and host > >that is supposed to be small over longer periods. Is that not > >achievable for > >a paravirtual guest?! I really need gettimeofday() calls to be > >near exactly > >the same value for applications in guest and host even after months. > > Except adding a hypercall to get host time (i.e. pv timer), or > using network time, I think cetain amount of shift will be always there. Do you consider that NTP between guest and host is acceptable? I found this btw: http://support.ntp.org/bin/view/Support/KnownOsIssues Quote: "It appears that Xen just passes time-related system calls to the underlying master domain, and does not require any additional changes to support time sync into the guest domains." When I today told my manager (technical background) about this, it was met with utter surprise, because "that should be really simple". Incidentally, I recently claimed in a meeting that with modern Linux and paravirtualization, this problem should no longer exist. Is this a design problem for KVM (the hypercall missing yet) or just something that the KVM community didn't yet have/find the time to get around to? Best regards, Kay ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
