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Dave Johnson edaf420fdc x86: fix TSC clock source calibration error 
I ran into this problem on a system that was unable to obtain NTP sync
because the clock was running very slow (over 10000ppm slow). ntpd had
declared all of its peers 'reject' with 'peer_dist' reason.

On investigation, the tsc_khz variable was significantly incorrect
causing xtime to run slow.  After a reboot tsc_khz was correct so I
did a reboot test to see how often the problem occurred:

Test was done on a 2000 Mhz Xeon system.  Of 689 reboots, 8 of them
had unacceptable tsc_khz values (>500ppm):

 range of tsc_khz  # of boots  % of boots
 ----------------  ----------  ----------
        < 1999750           0      0.000%
1999750 - 1999800          21      3.048%
1999800 - 1999850         166     24.128%
1999850 - 1999900         241     35.029%
1999900 - 1999950         211     30.669%
1999950 - 2000000          42      6.105%
2000000 - 2000000           0      0.000%
2000050 - 2000100           0      0.000%
                   [...]
2000100 - 2015000           1      0.145%  << BAD
2015000 - 2030000           6      0.872%  << BAD
2030000 - 2045000           1      0.145%  << BAD
2045000 <                   0      0.000%

The worst boot was 2032.577 Mhz, over 1.5% off!

It appears that on rare occasions, mach_countup() is taking longer to
complete than necessary.

I suspect that this is caused by the CPU taking a periodic SMI
interrupt right at the end of the 30ms calibration loop.  This would
cause the loop to delay while the SMI BIOS hander runs. The resulting
TSC value is beyond what it actually should be resulting in a higher
tsc_khz.

The below patch makes native_calculate_cpu_khz() take the best
(shortest duration, lowest khz) run of it's 3 calibration loops.  If a
SMI goes off causing a bad result (long duration, higher khz) it will
be discarded.

With the patch applied, 300 boots of the same system produce good
results:

 range of tsc_khz  # of boots  % of boots
 ----------------  ----------  ----------
        < 1999750           0      0.000%
1999750 - 1999800          30     10.000%
1999800 - 1999850         166     55.333%
1999850 - 1999900          89     29.667%
1999900 - 1999950          15      5.000%
1999950 <                   0      0.000%

Problem was found and tested against 2.6.18.  Patch is against 2.6.22.

Signed-off-by: Dave Johnson <djohnson@sw.starentnetworks.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2007-10-23 22:37:22 +02:00
..
acpi Merge git://git.kernel.org/pub/scm/linux/kernel/git/bunk/trivial 2007-10-19 20:36:17 -07:00
cpu Merge git://git.kernel.org/pub/scm/linux/kernel/git/bunk/trivial 2007-10-19 20:36:17 -07:00
.gitignore .gitignore update for x86 arch 2007-10-17 21:19:04 +02:00
alternative.c x86: convert cpuinfo_x86 array to a per_cpu array 2007-10-19 20:35:04 +02:00
aperture_64.c x86_64: move kernel 2007-10-11 11:17:24 +02:00
apic_32.c spelling fixes: arch/i386/ 2007-10-20 01:13:56 +02:00
apic_64.c x86: expand /proc/interrupts to include missing vectors, v2 2007-10-17 20:16:53 +02:00
apm_32.c spelling fixes: arch/i386/ 2007-10-20 01:13:56 +02:00
asm-offsets.c i386: move kernel 2007-10-11 11:17:01 +02:00
asm-offsets_32.c Boot with virtual == physical to get closer to native Linux. 2007-10-23 15:49:54 +10:00
asm-offsets_64.c x86_64: move kernel 2007-10-11 11:17:24 +02:00
audit_64.c x86_64: move kernel 2007-10-11 11:17:24 +02:00
bootflag.c i386: move kernel 2007-10-11 11:17:01 +02:00
bugs_64.c Delete filenames in comments. 2007-10-13 10:01:23 -07:00
cpuid.c x86: convert cpuinfo_x86 array to a per_cpu array 2007-10-19 20:35:04 +02:00
crash_32.c i386: move kernel 2007-10-11 11:17:01 +02:00
crash_64.c x86_64: move kernel 2007-10-11 11:17:24 +02:00
crash_dump_32.c kmap leak fix for x86_32 kdump 2007-10-19 11:53:33 -07:00
crash_dump_64.c Delete filenames in comments. 2007-10-13 10:01:23 -07:00
doublefault_32.c i386: move kernel 2007-10-11 11:17:01 +02:00
e820_32.c kexec: add BSS to resource tree 2007-10-22 08:13:19 -07:00
e820_64.c kexec: add BSS to resource tree 2007-10-22 08:13:19 -07:00
early-quirks.c x86: Unify i386 and x86-64 early quirks 2007-10-19 20:35:03 +02:00
early_printk.c [x86] remove uses of magic macros for boot_params access 2007-10-16 17:38:31 -07:00
efi_32.c kexec: add BSS to resource tree 2007-10-22 08:13:19 -07:00
efi_stub_32.S i386: move kernel 2007-10-11 11:17:01 +02:00
entry_32.S Merge branch 'xen-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen 2007-10-17 11:10:11 -07:00
entry_64.S x86: return correct error code from child_rip in x86_64 entry.S 2007-10-17 20:15:29 +02:00
genapic_64.c x86: convert cpu_to_apicid to be a per cpu variable 2007-10-19 20:35:03 +02:00
genapic_flat_64.c x86: convert cpu_to_apicid to be a per cpu variable 2007-10-19 20:35:03 +02:00
geode_32.c x86: Geode Multi-Function General Purpose Timers support 2007-10-12 23:04:06 +02:00
head64.c x86: use descriptor's functions instead of inline assembly 2007-10-19 20:35:03 +02:00
head_32.S i386: paravirt boot sequence 2007-10-22 08:13:17 -07:00
head_64.S x86_64: move kernel 2007-10-11 11:17:24 +02:00
hpet.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/bunk/trivial 2007-10-19 20:36:17 -07:00
i386_ksyms_32.c x86: convert mm_context_t semaphore to a mutex 2007-10-17 20:17:05 +02:00
i387_32.c Delete filenames in comments. 2007-10-13 10:01:23 -07:00
i387_64.c Delete filenames in comments. 2007-10-13 10:01:23 -07:00
i8237.c Delete filenames in comments. 2007-10-13 10:01:23 -07:00
i8253.c spelling fixes: arch/i386/ 2007-10-20 01:13:56 +02:00
i8259_32.c i386: introduce "used_vectors" bitmap which can be used to reserve vectors. 2007-10-19 20:35:03 +02:00
i8259_64.c x86: more struct irqaction initializer cleanups 2007-10-17 20:16:07 +02:00
init_task.c x86: merge init_task_32/64.c 2007-10-19 20:35:02 +02:00
io_apic_32.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/bunk/trivial 2007-10-19 20:36:17 -07:00
io_apic_64.c Intel IOMMU: DMAR fault handling support 2007-10-22 08:13:19 -07:00
ioport_32.c Delete filenames in comments. 2007-10-13 10:01:23 -07:00
ioport_64.c Delete filenames in comments. 2007-10-13 10:01:23 -07:00
irq_32.c x86: also show non-zero IRQ counts for vectors that currently don't have a handler 2007-10-17 20:16:54 +02:00
irq_64.c x86: also show non-zero IRQ counts for vectors that currently don't have a handler 2007-10-17 20:16:54 +02:00
k8.c x86_64: move kernel 2007-10-11 11:17:24 +02:00
kprobes_32.c kprobes: support kretprobe blacklist 2007-10-16 09:43:10 -07:00
kprobes_64.c kprobes: support kretprobe blacklist 2007-10-16 09:43:10 -07:00
ldt_32.c x86: convert mm_context_t semaphore to a mutex 2007-10-17 20:17:05 +02:00
ldt_64.c x86: convert mm_context_t semaphore to a mutex 2007-10-17 20:17:00 +02:00
machine_kexec_32.c Use extended crashkernel command line on i386 2007-10-19 11:53:49 -07:00
machine_kexec_64.c Use extended crashkernel command line on x86_64 2007-10-19 11:53:50 -07:00
Makefile x86: delete vsyscall files during make clean 2007-10-17 21:56:01 +02:00
Makefile_32 x86: Unify i386 and x86-64 early quirks 2007-10-19 20:35:03 +02:00
Makefile_64 x86: Unify i386 and x86-64 early quirks 2007-10-19 20:35:03 +02:00
mca_32.c Delete filenames in comments. 2007-10-13 10:01:23 -07:00
mce_64.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/bunk/trivial 2007-10-19 20:36:17 -07:00
mce_amd_64.c x86: convert cpuinfo_x86 array to a per_cpu array 2007-10-19 20:35:04 +02:00
mce_intel_64.c x86: expand /proc/interrupts to include missing vectors, v2 2007-10-17 20:16:53 +02:00
mfgpt_32.c x86: Geode MFGPT clock event device support 2007-10-12 23:04:06 +02:00
microcode.c x86: convert cpuinfo_x86 array to a per_cpu array 2007-10-19 20:35:04 +02:00
module_32.c i386: move kernel 2007-10-11 11:17:01 +02:00
module_64.c x86_64: move kernel 2007-10-11 11:17:24 +02:00
mpparse_32.c spelling fixes: arch/i386/ 2007-10-20 01:13:56 +02:00
mpparse_64.c x86: acpi use cpu_physical_id 2007-10-19 20:35:03 +02:00
msr.c x86: convert cpuinfo_x86 array to a per_cpu array 2007-10-19 20:35:04 +02:00
nmi_32.c x86: Fix irq0 / local apic timer accounting 2007-10-12 23:04:06 +02:00
nmi_64.c x86: Fix irq0 / local apic timer accounting 2007-10-12 23:04:07 +02:00
numaq_32.c i386: move kernel 2007-10-11 11:17:01 +02:00
paravirt_32.c paravirt: clean up lazy mode handling 2007-10-16 11:51:29 -07:00
pci-calgary_64.c Update arch/ to use sg helpers 2007-10-22 21:19:59 +02:00
pci-dma_32.c i386: Clean up duplicate includes in arch/i386/kernel/ 2007-10-17 20:15:51 +02:00
pci-dma_64.c Intel IOMMU: Intel IOMMU driver 2007-10-22 08:13:18 -07:00
pci-gart_64.c Update arch/ to use sg helpers 2007-10-22 21:19:59 +02:00
pci-nommu_64.c Update arch/ to use sg helpers 2007-10-22 21:19:59 +02:00
pci-swiotlb_64.c x86_64: move kernel 2007-10-11 11:17:24 +02:00
pcspeaker.c i386: move kernel 2007-10-11 11:17:01 +02:00
pmtimer_64.c x86_64: move kernel 2007-10-11 11:17:24 +02:00
process_32.c Merge ssh://master.kernel.org/pub/scm/linux/kernel/git/tglx/linux-2.6-x86 2007-10-19 15:06:00 -07:00
process_64.c kprobes: support kretprobe blacklist 2007-10-16 09:43:10 -07:00
ptrace_32.c spelling fixes: arch/i386/ 2007-10-20 01:13:56 +02:00
ptrace_64.c x86: convert mm_context_t semaphore to a mutex 2007-10-17 20:17:00 +02:00
quirks.c x86: enable HPET on ICH3 and ICH4 2007-10-19 20:35:02 +02:00
reboot_32.c Merge branch 'dmi-const' of git://git.kernel.org/pub/scm/linux/kernel/git/jgarzik/misc-2.6 2007-10-11 19:18:45 -07:00
reboot_64.c x86: use descriptor's functions instead of inline assembly 2007-10-19 20:35:03 +02:00
reboot_fixups_32.c GEODE: use symbolic constant in cs5536 reboot fixup 2007-10-19 20:35:02 +02:00
relocate_kernel_32.S i386: move kernel 2007-10-11 11:17:01 +02:00
relocate_kernel_64.S x86_64: move kernel 2007-10-11 11:17:24 +02:00
scx200_32.c long vs. unsigned long - low-hanging fruits in drivers 2007-10-14 12:41:51 -07:00
setup64.c x86: use descriptor's functions instead of inline assembly 2007-10-19 20:35:03 +02:00
setup_32.c kexec: add BSS to resource tree 2007-10-22 08:13:19 -07:00
setup_64.c kexec: add BSS to resource tree 2007-10-22 08:13:19 -07:00
sigframe_32.h i386: move kernel 2007-10-11 11:17:01 +02:00
signal_32.c spelling fixes: arch/i386/ 2007-10-20 01:13:56 +02:00
signal_64.c spelling fixes: arch/x86_64/ 2007-10-20 01:25:36 +02:00
smp_32.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/bunk/trivial 2007-10-19 20:36:17 -07:00
smp_64.c x86: implement missing x86_64 function smp_call_function_mask() 2007-10-19 20:35:03 +02:00
smpboot_32.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/bunk/trivial 2007-10-19 20:36:17 -07:00
smpboot_64.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/bunk/trivial 2007-10-19 20:36:17 -07:00
smpcommon_32.c i386: move kernel 2007-10-11 11:17:01 +02:00
srat_32.c i386: move kernel 2007-10-11 11:17:01 +02:00
stacktrace.c x86: constify stacktrace_ops 2007-10-17 20:16:11 +02:00
summit_32.c spelling fixes: arch/i386/ 2007-10-20 01:13:56 +02:00
suspend_64.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/bunk/trivial 2007-10-19 20:36:17 -07:00
suspend_asm_64.S Hibernation: Pass CR3 in the image header on x86_64 2007-10-18 14:37:19 -07:00
sys_i386_32.c remove include/asm-*/ipc.h 2007-10-17 08:42:55 -07:00
sys_x86_64.c Delete filenames in comments. 2007-10-13 10:01:23 -07:00
syscall_64.c i386/x86_64: move headers to include/asm-x86 2007-10-11 11:20:03 +02:00
syscall_table_32.S i386: move kernel 2007-10-11 11:17:01 +02:00
sysenter_32.c Delete filenames in comments. 2007-10-13 10:01:23 -07:00
tce_64.c x86: Create clflush() inline, remove hardcoded wbinvd 2007-10-17 20:16:12 +02:00
time_32.c x86: Fix irq0 / local apic timer accounting 2007-10-12 23:04:06 +02:00
time_64.c x86_64: remove now unused code 2007-10-12 23:04:23 +02:00
topology.c i386: no need to make enable_cpu_hotplug a variable 2007-10-17 20:16:16 +02:00
trampoline_32.S x86: misc. constifications 2007-10-17 20:16:08 +02:00
trampoline_64.S x86: misc. constifications 2007-10-17 20:16:08 +02:00
traps_32.c Merge ssh://master.kernel.org/pub/scm/linux/kernel/git/tglx/linux-2.6-x86 2007-10-19 15:06:00 -07:00
traps_64.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/bunk/trivial 2007-10-19 20:36:17 -07:00
tsc_32.c x86: fix TSC clock source calibration error 2007-10-23 22:37:22 +02:00
tsc_64.c x86: convert cpuinfo_x86 array to a per_cpu array 2007-10-19 20:35:04 +02:00
tsc_sync.c Delete filenames in comments. 2007-10-13 10:01:23 -07:00
verify_cpu_64.S x86_64: move kernel 2007-10-11 11:17:24 +02:00
vm86_32.c Delete filenames in comments. 2007-10-13 10:01:23 -07:00
vmi_32.c paravirt: clean up lazy mode handling 2007-10-16 11:51:29 -07:00
vmiclock_32.c i386: move kernel 2007-10-11 11:17:01 +02:00
vmlinux.lds.S i386: move kernel 2007-10-11 11:17:01 +02:00
vmlinux_32.lds.S i386: move kernel 2007-10-11 11:17:01 +02:00
vmlinux_64.lds.S x86_64: move kernel 2007-10-11 11:17:24 +02:00
vsmp_64.c x86_64: move kernel 2007-10-11 11:17:24 +02:00
vsyscall-int80_32.S i386: move kernel 2007-10-11 11:17:01 +02:00
vsyscall-note_32.S i386: move kernel 2007-10-11 11:17:01 +02:00
vsyscall-sigreturn_32.S i386: move kernel 2007-10-11 11:17:01 +02:00
vsyscall-sysenter_32.S i386: move kernel 2007-10-11 11:17:01 +02:00
vsyscall_32.lds.S i386: move kernel 2007-10-11 11:17:01 +02:00
vsyscall_32.S i386: move kernel 2007-10-11 11:17:01 +02:00
vsyscall_64.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/bunk/trivial 2007-10-19 20:36:17 -07:00
x8664_ksyms_64.c x86_64: move kernel 2007-10-11 11:17:24 +02:00