OK, so the local APIC timer is not working as I expected. Perhaps it's not wired up to produce the timer interrupt as we expect.
I've disabled the Local APIC timer and lo and behold it works fine: ./clocktest Testing for clock jitter on 8 cpus PASSED: largest jitter seen was 0.001365 Testing clock direction for 5 minutes... PASSED: Iteration 0 delta: 0.000447 PASSED: Iteration 1 delta: 0.001461 PASSED: Iteration 2 delta: 0.001509 PASSED: Iteration 3 delta: 0.001465 PASSED: Iteration 4 delta: 0.001416 clock direction test: sleeptime 60 sec per iteration, failed iterations: 0 So much hunch is that there is something wrong in the firmware not setting up the APIC IRQ routing and hence we're not getting wakeups from the APICS causing the poor scheduling wakeup responses when the CPUs go into an idle state. As it stands, I believe there is something not correct with the way the timer interrupts being configured, which is certainly BIOS related. I think we need an AMD APIC expert and/or somebody with the IRQ firmware routing know-how to verify this assertion. BTW, the kernel is reporting that 4 of the ACPI _PRS objects are not correctly configured: <4>[ 3.114961] ACPI: Invalid _PRS IRQ 0 <6>[ 3.115192] ACPI: PCI Interrupt Link [U1PI] (IRQs) *0 <4>[ 3.115613] ACPI: Invalid _PRS IRQ 0 <6>[ 3.115846] ACPI: PCI Interrupt Link [U2PI] (IRQs) *0 <4>[ 3.116244] ACPI: Invalid _PRS IRQ 0 <6>[ 3.116484] ACPI: PCI Interrupt Link [U3PI] (IRQs) *0 <4>[ 3.116891] ACPI: Invalid _PRS IRQ 0 <6>[ 3.117147] ACPI: PCI Interrupt Link [U4PI] (IRQs) *0 <6>[ 3.117439] ACPI: PCI Interrupt Link [SATA] (IRQs *16) <4>[ 3.117745] ACPI: Invalid _PRS IRQ 0 so this looks iffy too. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1564949 Title: Severe latency/skew on AMD Opetron processor To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1564949/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
