Re: [Xen-devel] clock source in PV Linux
On 12/18/19 12:36 AM, Roman Shaposhnik wrote: On Wed, Dec 11, 2019 at 12:41 AM Jan Beulich wrote: On 11.12.2019 09:16, Jürgen Groß wrote: On 11.12.19 08:28, Jan Beulich wrote: Jürgen, Boris, I've noticed <6>clocksource: Switched to clocksource tsc as the final clocksource related boot message in a PV Dom0's log with 5.4.2. Is it intentional that it's not the "xen" one that gets used by default? I think this is fine. I just tested it and I'm seeing the same in dom0, while in a PV domU "xen" is used per default. In dom0 "tsc" should be okay in case it is stable. Or are you expecting problems with that setting? Well, first of all I found this surprising. Whether there are problems to be expected largely depends on the reliability of the "stable" detection in PV Dom0. Related question: does this mean that tsc is now default for PVH as well? The reason I'm asking is because I'm still a bit worried about the clock drift with tsc. dom0 will use TSC for either PV or PVH: xen_time_init(): /* As Dom0 is never moved, no penalty on using TSC there */ if (xen_initial_domain()) xen_clocksource.rating = 275; But as far as TSC stability I'd think it should be sufficiently checked by generic TSC init code? -boris ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
Re: [Xen-devel] clock source in PV Linux
On Wed, Dec 11, 2019 at 12:41 AM Jan Beulich wrote: > > On 11.12.2019 09:16, Jürgen Groß wrote: > > On 11.12.19 08:28, Jan Beulich wrote: > >> Jürgen, Boris, > >> > >> I've noticed > >> > >> <6>clocksource: Switched to clocksource tsc > >> > >> as the final clocksource related boot message in a PV Dom0's > >> log with 5.4.2. Is it intentional that it's not the "xen" one > >> that gets used by default? > > > > I think this is fine. I just tested it and I'm seeing the same in dom0, > > while in a PV domU "xen" is used per default. > > > > In dom0 "tsc" should be okay in case it is stable. Or are you expecting > > problems with that setting? > > Well, first of all I found this surprising. Whether there are problems to > be expected largely depends on the reliability of the "stable" detection > in PV Dom0. Related question: does this mean that tsc is now default for PVH as well? The reason I'm asking is because I'm still a bit worried about the clock drift with tsc. Thanks, Roman. ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
Re: [Xen-devel] clock source in PV Linux
On 11.12.2019 09:16, Jürgen Groß wrote: > On 11.12.19 08:28, Jan Beulich wrote: >> Jürgen, Boris, >> >> I've noticed >> >> <6>clocksource: Switched to clocksource tsc >> >> as the final clocksource related boot message in a PV Dom0's >> log with 5.4.2. Is it intentional that it's not the "xen" one >> that gets used by default? > > I think this is fine. I just tested it and I'm seeing the same in dom0, > while in a PV domU "xen" is used per default. > > In dom0 "tsc" should be okay in case it is stable. Or are you expecting > problems with that setting? Well, first of all I found this surprising. Whether there are problems to be expected largely depends on the reliability of the "stable" detection in PV Dom0. Jan ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
Re: [Xen-devel] clock source in PV Linux
On 11.12.19 08:28, Jan Beulich wrote: Jürgen, Boris, I've noticed <6>clocksource: Switched to clocksource tsc as the final clocksource related boot message in a PV Dom0's log with 5.4.2. Is it intentional that it's not the "xen" one that gets used by default? I think this is fine. I just tested it and I'm seeing the same in dom0, while in a PV domU "xen" is used per default. In dom0 "tsc" should be okay in case it is stable. Or are you expecting problems with that setting? Juergen ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
[Xen-devel] clock source in PV Linux
Jürgen, Boris, I've noticed <6>clocksource: Switched to clocksource tsc as the final clocksource related boot message in a PV Dom0's log with 5.4.2. Is it intentional that it's not the "xen" one that gets used by default? Thanks, Jan ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
