ia64/linux-2.6.18-xen.hg

view Documentation/time_interpolators.txt @ 452:c7ed6fe5dca0

kexec: dont initialise regions in reserve_memory()

There is no need to initialise efi_memmap_res and boot_param_res in
reserve_memory() for the initial xen domain as it is done in
machine_kexec_setup_resources() using values from the kexec hypercall.

Signed-off-by: Simon Horman <horms@verge.net.au>
author Keir Fraser <keir.fraser@citrix.com>
date Thu Feb 28 10:55:18 2008 +0000 (2008-02-28)
parents 831230e53067
children
line source
1 Time Interpolators
2 ------------------
4 Time interpolators are a base of time calculation between timer ticks and
5 allow an accurate determination of time down to the accuracy of the time
6 source in nanoseconds.
8 The architecture specific code typically provides gettimeofday and
9 settimeofday under Linux. The time interpolator provides both if an arch
10 defines CONFIG_TIME_INTERPOLATION. The arch still must set up timer tick
11 operations and call the necessary functions to advance the clock.
13 With the time interpolator a standardized interface exists for time
14 interpolation between ticks. The provided logic is highly scalable
15 and has been tested in SMP situations of up to 512 CPUs.
17 If CONFIG_TIME_INTERPOLATION is defined then the architecture specific code
18 (or the device drivers - like HPET) may register time interpolators.
19 These are typically defined in the following way:
21 static struct time_interpolator my_interpolator {
22 .frequency = MY_FREQUENCY,
23 .source = TIME_SOURCE_MMIO32,
24 .shift = 8, /* scaling for higher accuracy */
25 .drift = -1, /* Unknown drift */
26 .jitter = 0 /* time source is stable */
27 };
29 void time_init(void)
30 {
31 ....
32 /* Initialization of the timer *.
33 my_interpolator.address = &my_timer;
34 register_time_interpolator(&my_interpolator);
35 ....
36 }
38 For more details see include/linux/timex.h and kernel/timer.c.
40 Christoph Lameter <christoph@lameter.com>, October 31, 2004