Bogomips incorrect on second core

[Graham Maltby]

Binary package hint: linux-image-2.6.28-11-generic

I recently did a network upgrade from 8.10 to 9.04. The system has a Pentium D 3.2GHz CPU. After the upgrade the installed kernel was 2.6.28-11.

This kernel is calibrating the bogomips differently between the two cores. The first core is correct and reports at 6401.xx but the second core varies widely. I've seen it as low as 4680 and as high as 13251.

'cat /proc/cpuinfo'

processor : 0
bogomips : 6401.67
processor : 1
bogomips : 13251.02

After a reboot:

processor : 0
bogomips : 6401.65
processor : 1
bogomips : 5916.13

Reverting to 2.6.27-11-generic gives a consistent result always.

processor : 0
bogomips : 6401.67
processor : 1
bogomips : 6401.88

The symptoms:
-- poor system stability with occasional lockups;
-- poor performance - although I'm not sure how to confirm it, I assume the system is expecting more from the "faster" core and not getting it;
-- powernowd doesn't seem to register that there is load so never increases the clocking.

This issue is reproducible but the system is semi-production so the options for testing are limited. If you require further information, let me know and I'll see what I can get.

[Lucas Gadani (lgadani)]

This is also happening to me. Sometimes bogomips are wrongly calculated, please see attached file. CPU is a Core 2 Quad Q6600 (overclocked to 3.4GHz). I can provide more details if needed.

I don't see any symptons, just discovered accidentally.

[Graham Maltby (gmaltby)]

The most recent kernel (2.6.28-13-generic) does not appear to have this problem.

[Jeremy Foshee (jeremyfoshee)]

Hi Graham,

This bug was reported a while ago and there hasn't been any activity in it recently. We were wondering if this is still an issue? Can you try with the latest development release of Ubuntu? ISO CD images are available from http://cdimage.ubuntu.com/releases/lucid.

If it remains an issue, could you run the following command from a Terminal (Applications->Accessories->Terminal). It will automatically gather and attach updated debug information to this report.

apport-collect -p linux 375791

Also, if you could test the latest upstream kernel available that would be great. It will allow additional upstream developers to examine the issue. Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Once you've tested the upstream kernel, please remove the 'needs-upstream-testing' tag. This can be done by clicking on the yellow pencil icon next to the tag located at the bottom of the bug description and deleting the 'needs-upstream-testing' text. Please let us know your results.

Thanks in advance.

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[Jeremy Foshee (jeremyfoshee)]

This bug report was marked as Incomplete and has not had any updated comments for quite some time. As a result this bug is being closed. Please reopen if this is still an issue in the current Ubuntu release http://www.ubuntu.com/getubuntu/download . Also, please be sure to provide any requested information that may have been missing. To reopen the bug, click on the current status under the Status column and change the status back to "New". Thanks.

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