Messages in this thread | | | Date | Thu, 08 May 2008 12:40:54 +0200 | From | Philipp Kohlbecher <> | Subject | clocksources: order of preference |
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Why is the TSC preferred to the HPET as a clocksource for the x86 architecture?
"Understanding the Linux Kernel" states that the HPET is preferable to the TSC due to its richer architecture. Up to version 2.6.17.14, arch/i386/kernel/timers/timer.c also contained a comment to that effect and accordingly ranked the HPET before the TSC.
This was changed when the new clocksource infrastructure was introduced with version 2.6.18. (The HPET clocksource received a rating of 250; the TSC, 300.)
Preferring the TSC leads to problems when it is unstable. While this can be prevented by setting CONFIG_X86_TSC, certain distribution kernels (striving for compatibility) don't, resulting in soft lockups.
Are there better reasons to prefer the TSC or may I submit a patch that swaps the respective ratings?
Thanks for reading, - Philipp Kohlbecher
Please CC me, I am not on the list.
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