Re: recalibrating x86 TSC during suspend/resume

2019-02-22 Thread Olaf Hering
On Fri, Feb 22, Paolo Bonzini wrote: > On 22/02/19 12:44, Thomas Gleixner wrote: > >> The specific usecase I have is a workload within VMs that makes heavy > >> use of TSC. The kernel is booted with 'clocksource=tsc highres=off > >> nohz=off' > >> because only this clocksource gives enough granul

Re: recalibrating x86 TSC during suspend/resume

2019-02-22 Thread Paolo Bonzini
On 22/02/19 12:44, Thomas Gleixner wrote: >> The specific usecase I have is a workload within VMs that makes heavy >> use of TSC. The kernel is booted with 'clocksource=tsc highres=off nohz=off' >> because only this clocksource gives enough granularity. The default >> paravirtualized clock will ret

Re: recalibrating x86 TSC during suspend/resume

2019-02-22 Thread Olaf Hering
Am Fri, 22 Feb 2019 12:44:39 +0100 (CET) schrieb Thomas Gleixner : > Whether that is accurate enough or not to make NTP happy, I can't tell, but > it's definitely worth a try. Thanks Thomas, I will look into the suggestions. Olaf pgpKvKEGb9vSF.pgp Description: Digitale Signatur von OpenPGP

Re: recalibrating x86 TSC during suspend/resume

2019-02-22 Thread Thomas Gleixner
On Fri, 22 Feb 2019, Olaf Hering wrote: > Is there a way to recalibrate the x86 TSC during a suspend/resume cycle? No. > While the frequency will remain the same on a Laptop, it may (or rather: > it definitly will) differ if a VM is migrated from one host to another. > The hypervisor may choose t

recalibrating x86 TSC during suspend/resume

2019-02-22 Thread Olaf Hering
Is there a way to recalibrate the x86 TSC during a suspend/resume cycle? While the frequency will remain the same on a Laptop, it may (or rather: it definitly will) differ if a VM is migrated from one host to another. The hypervisor may choose to emulate the expected TSC frequency on the destinati