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08ec0c58fb
linux/arch/x86/kernel
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John Stultz 08ec0c58fb x86: Improve TSC calibration using a delayed workqueue 
Boot to boot the TSC calibration may vary by quite a large amount.

While normal variance of 50-100ppm can easily be seen, the quick
calibration code only requires 500ppm accuracy, which is the limit
of what NTP can correct for.

This can cause problems for systems being used as NTP servers, as
every time they reboot it can take hours for them to calculate the
new drift error caused by the calibration.

The classic trade-off here is calibration accuracy vs slow boot times,
as during the calibration nothing else can run.

This patch uses a delayed workqueue  to calibrate the TSC over the
period of a second. This allows very accurate calibration (in my
tests only varying by 1khz or 0.4ppm boot to boot). Additionally this
refined calibration step does not block the boot process, and only
delays the TSC clocksoure registration by a few seconds in early boot.
If the refined calibration strays 1% from the early boot calibration
value, the system will fall back to already calculated early boot
calibration.

Credit to Andi Kleen who suggested using a timer quite awhile back,
but I dismissed it thinking the timer calibration would be done after
the clocksource was registered (which would break things). Forgive
me for my short-sightedness.

This patch has worked very well in my testing, but TSC hardware is
quite varied so it would probably be good to get some extended
testing, possibly pushing inclusion out to 2.6.39.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
LKML-Reference: <1289003985-29060-1-git-send-email-johnstul@us.ibm.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Ingo Molnar <mingo@elte.hu>
CC: Martin Schwidefsky <schwidefsky@de.ibm.com>
CC: Clark Williams <williams@redhat.com>
CC: Andi Kleen <andi@firstfloor.org>
2010-12-02 16:48:37 -08:00
..
acpi Merge branch 'stable/xen-pcifront-0.8.2' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen 2010-10-28 17:11:17 -07:00
apic x86, apic: Remove double #include 2010-11-10 10:21:16 +01:00
cpu perf, amd: Use kmalloc_node(,__GFP_ZERO) for northbridge structure allocation 2010-11-10 22:58:40 +01:00
.gitignore
alternative.c Merge branches 'perf-fixes-for-linus' and 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-10-30 11:43:26 -07:00
amd_iommu_init.c Merge branch 'x86-iommu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-10-21 14:23:48 -07:00
amd_iommu.c x86/amd-iommu: Update copyright headers 2010-10-13 11:13:21 +02:00
amd_nb.c x86, amd_nb: Enable GART support for AMD family 0x15 CPUs 2010-10-01 16:18:32 -07:00
apb_timer.c Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-10-21 14:11:46 -07:00
aperture_64.c Merge branch 'x86-iommu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-10-21 14:23:48 -07:00
apm_32.c Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2010-10-24 13:41:39 -07:00
asm-offsets_32.c x86, asm: Fix CFI macro invocations to deal with shortcomings in gas 2010-10-19 14:28:02 -07:00
asm-offsets_64.c
asm-offsets.c
audit_64.c
bootflag.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
check.c x86: Use memblock to replace early_res 2010-08-27 11:12:29 -07:00
cpuid.c BKL: remove extraneous #include <smp_lock.h> 2010-11-17 08:59:32 -08:00
crash_dump_32.c mm: stack based kmap_atomic() 2010-10-26 16:52:08 -07:00
crash_dump_64.c mm, x86: Saving vmcore with non-lazy freeing of vmas 2010-09-17 09:11:56 +02:00
crash.c x86, UV: Make kdump avoid stack dumps 2010-07-21 11:33:27 -07:00
doublefault_32.c
dumpstack_32.c x86, printk: Get rid of <0> from stack output 2010-10-23 20:03:03 +02:00
dumpstack_64.c x86, printk: Get rid of <0> from stack output 2010-10-23 20:03:03 +02:00
dumpstack.c x86: Unify dumpstack.h and stacktrace.h 2010-06-08 23:29:52 +02:00
e820.c x86, memblock: Use memblock_memory_size()/memblock_free_memory_size() to get correct dma_reserve 2010-08-27 11:13:54 -07:00
early_printk_mrst.c x86, earlyprintk: Add hsu early console for Intel Medfield platform 2010-10-08 10:01:47 +02:00
early_printk.c x86, earlyprintk: Add hsu early console for Intel Medfield platform 2010-10-08 10:01:47 +02:00
early-quirks.c Merge branch 'x86-cleanups-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-10-21 13:18:06 -07:00
entry_32.S x86, asm: Restore parentheses around one pushl_cfi argument 2010-10-22 10:51:44 +02:00
entry_64.S Merge branches 'softirq-for-linus', 'x86-debug-for-linus', 'x86-numa-for-linus', 'x86-quirks-for-linus', 'x86-setup-for-linus', 'x86-uv-for-linus' and 'x86-vm86-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-10-23 08:25:36 -07:00
ftrace.c jump label: Make dynamic no-op selection available outside of ftrace 2010-09-20 18:19:39 -04:00
head32.c Merge branch 'x86-trampoline-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-10-22 20:37:50 -07:00
head64.c x86-64: Only set max_pfn_mapped to 512 MiB if we enter via head_64.S 2010-10-14 09:06:49 +02:00
head_32.S x86-32, mm: Add an initial page table for core bootstrapping 2010-10-20 14:23:55 -07:00
head_64.S x86-64: Simplify loading initial_gs 2010-07-21 21:23:51 -07:00
head.c x86: Use memblock to replace early_res 2010-08-27 11:12:29 -07:00
hpet.c workqueues: s/ON_STACK/ONSTACK/ 2010-10-26 16:52:14 -07:00
hw_breakpoint.c x86: Fix instruction breakpoint encoding 2010-09-17 03:24:13 +02:00
i386_ksyms_32.c
i387.c Merge branch 'x86-fpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-10-21 13:34:32 -07:00
i8237.c
i8253.c i8253: Convert i8253_lock to raw_spinlock 2010-03-02 10:28:38 +01:00
i8259.c x86: i8259: Convert to new irq_chip functions 2010-10-12 16:53:36 +02:00
init_task.c Rename .data.cacheline_aligned to .data..cacheline_aligned. 2010-03-03 11:25:58 +01:00
io_delay.c
ioport.c
irq_32.c x86-32: Restore irq stacks NUMA-aware allocations 2010-10-29 08:17:07 +02:00
irq_64.c
irq_work.c irq_work: Add generic hardirq context callbacks 2010-10-18 19:58:50 +02:00
irq.c Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-10-21 14:11:46 -07:00
irqinit.c Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-10-21 14:11:46 -07:00
jump_label.c jump label: x86 support 2010-09-22 16:33:03 -04:00
kdebugfs.c llseek: automatically add .llseek fop 2010-10-15 15:53:27 +02:00
kgdb.c kgdb,x86: fix regression in detach handling 2010-11-17 13:54:57 -06:00
kprobes.c jump label: Add jump_label_text_reserved() to reserve jump points 2010-09-22 16:30:46 -04:00
kvm.c
kvmclock.c KVM guest: Move a printk that's using the clock before it's ready 2010-10-24 10:53:06 +02:00
ldt.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
machine_kexec_32.c
machine_kexec_64.c x86, cleanups: Use clear_page/copy_page rather than memset/memcpy 2010-09-22 15:36:49 -07:00
Makefile x86: Move olpc to platform 2010-10-27 17:22:16 +02:00
mca_32.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
microcode_amd.c x86: Remove unnecessary casts of void ptr returning alloc function return values 2010-11-10 09:13:00 +01:00
microcode_core.c Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2010-10-24 13:41:39 -07:00
microcode_intel.c Update broken web addresses in arch directory. 2010-10-18 11:03:21 +02:00
mmconf-fam10h_64.c x86: Adjust section annotations in AMD Fam10 MMCONF enabling code 2010-11-10 10:08:26 +01:00
module.c Merge commit 'v2.6.36-rc7' into perf/core 2010-10-08 10:46:27 +02:00
mpparse.c Merge commit 'v2.6.36-rc3' into x86/memblock 2010-08-31 09:45:46 +02:00
msr.c BKL: remove extraneous #include <smp_lock.h> 2010-11-17 08:59:32 -08:00
paravirt_patch_32.c
paravirt_patch_64.c
paravirt-spinlocks.c
paravirt.c x86, paravirt: Remove alloc_pmd_clone hook, only used by VMI 2010-08-23 17:09:44 -07:00
pci-calgary_64.c x86, calgary: Make Calgary IOMMU use IOMMU_INIT_* macros. 2010-08-26 15:14:15 -07:00
pci-dma.c x86, iommu: Utilize the IOMMU_INIT macros functionality. 2010-08-26 15:14:52 -07:00
pci-gart_64.c Merge branch 'x86-iommu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-10-21 14:23:48 -07:00
pci-iommu_table.c x86, iommu: Add proper dependency sort routine (and sanity check). 2010-08-26 15:13:19 -07:00
pci-nommu.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
pci-swiotlb.c x86, swiotlb: Make SWIOTLB use IOMMU_INIT_* macros. 2010-08-26 15:13:37 -07:00
pcspeaker.c
probe_roms_32.c
process_32.c x86, perf: Add power_end event to process_*.c cpu_idle routine 2010-06-18 11:35:10 +02:00
process_64.c x86-64, fpu: Disable preemption when using TS_USEDFPU 2010-09-09 14:16:45 -07:00
process.c Make do_execve() take a const filename pointer 2010-08-17 18:07:43 -07:00
ptrace.c ptrace: cleanup arch_ptrace() on x86 2010-10-27 18:03:10 -07:00
pvclock.c x86, pvclock: Remove leftover scale_delta() function 2010-11-10 10:32:15 +01:00
quirks.c x86: HPET force enable for CX700 / VIA Epia LT 2010-09-15 16:27:04 +02:00
reboot_fixups_32.c
reboot.c Merge branch 'linus' into x86/urgent 2010-10-25 19:38:52 +02:00
relocate_kernel_32.S
relocate_kernel_64.S
rtc.c
setup_percpu.c Merge branch 'core-memblock-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-10-21 18:52:11 -07:00
setup.c Merge branch 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci-2.6 2010-10-28 11:59:52 -07:00
signal.c
smp.c x86, kexec: Make sure to stop all CPUs before exiting the kernel 2010-10-21 13:30:44 -07:00
smpboot.c Merge branch 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-10-27 18:38:55 -07:00
stacktrace.c x86: Unify save_stack_address() and save_stack_address_nosched() 2010-06-09 17:32:19 +02:00
step.c x86, ptrace: Fix block-step 2010-03-26 11:33:57 +01:00
sys_i386_32.c i386: Make kernel_execve() suitable for stack unwinding 2010-09-03 08:16:02 +02:00
sys_x86_64.c improve sys_newuname() for compat architectures 2010-03-12 15:52:32 -08:00
syscall_64.c
syscall_table_32.S x86: fix up system call numbering nit 2010-08-10 15:35:10 -07:00
tboot.c Merge branch 'kvm-updates/2.6.35' of git://git.kernel.org/pub/scm/virt/kvm/kvm 2010-05-21 17:16:21 -07:00
tce_64.c
test_nx.c
test_rodata.c
time.c
tls.c
tls.h
topology.c
trampoline_32.S
trampoline_64.S
trampoline.c Merge branch 'x86-trampoline-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-10-22 20:37:50 -07:00
traps.c Merge branches 'softirq-for-linus', 'x86-debug-for-linus', 'x86-numa-for-linus', 'x86-quirks-for-linus', 'x86-setup-for-linus', 'x86-uv-for-linus' and 'x86-vm86-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-10-23 08:25:36 -07:00
tsc_sync.c
tsc.c x86: Improve TSC calibration using a delayed workqueue 2010-12-02 16:48:37 -08:00
verify_cpu_64.S x86: Use symbolic MSR names 2010-07-21 21:23:40 -07:00
vm86_32.c x86, vm86: Fix preemption bug for int1 debug and int3 breakpoint handlers. 2010-09-23 11:07:49 -07:00
vmlinux.lds.S Merge branch 'x86-irq-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-10-22 08:54:21 -07:00
vsmp_64.c
vsyscall_64.c timkeeping: Fix update_vsyscall to provide wall_to_monotonic offset 2010-07-27 12:40:54 +02:00
x86_init.c x86: Introduce x86_msi_ops 2010-10-18 10:49:34 -04:00
x8664_ksyms_64.c x86-64: Don't export init_level4_pgt 2010-04-28 17:25:47 -07:00
xsave.c Merge branch 'x86-xsave-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-08-06 16:25:13 -07:00