01-08-2008
kernel:how to modify and read the tick rate:HZ
hi,
one of our customer is facing an issue with jiffies wrap up.
on a 32 bit machine, the variable jiffies count upto 472 days.
the customer's server was up for 472 days ('uptime') and to reproduce
the same, i tried to change the variable HZ in linux-2.6..23.9/include/asm-i386/param.h
from 100 to 10000.
after which i rebuilt the kernel with following steps:
# make oldconfig
# make modules_install
# make install
Now when i boot from this newly built kernel, i wrote a small kernel module
to read the jiffies and HZ global variable,which is as follows:
[root@localhost drivers]# cat get_jiffies.c
#include <linux/init.h>
#include <linux/module.h>
#include <asm/current.h>
#include <linux/sched.h>
#include <linux/time.h>
#include <linux/jiffies.h>
static int __init jiffies_init(void)
{
unsigned long j,z;
j = z = 0;
j = jiffies;
z = HZ;
printk(KERN_ALERT "jiffies value is %lu\n",j);
printk(KERN_ALERT "jiffies value in seconds %lu\n",(jiffies/HZ));
printk(KERN_ALERT "HZ value is %lu\n",z);
return 0;
}
static void __exit jiffies_exit(void)
{
printk(KERN_ALERT "Goodbye, world!\n");
}
module_init(jiffies_init);
module_exit(jiffies_exit);
MODULE_LICENSE("GPL");
[root@localhost drivers]# insmod get_jiffies.ko
[root@localhost drivers]# dmesg
jiffies value is 372939
jiffies value in seconds 1491
HZ value is 250 <====
why this HZ variable is shown as 250 ?
i am a newbie in kernel programming and i might be doing something really stupid as well.
~amit
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fruadm(1M) System Administration Commands fruadm(1M)
NAME
fruadm - prints and updates customer data associated with FRUs
SYNOPSIS
/usr/platform/sun4u/sbin/fruadm
/usr/platform/sun4u/sbin/fruadm -l
/usr/platform/sun4u/sbin/fruadm [-r] path [text]
DESCRIPTION
fruadm prints or sets the customer data for Field-Replaceable Units (FRUs).
Without arguments, fruadm prints the paths of all FRU ID-capable FRUs (containers) in the system, along with the contents of the customer
data record, if present, for each such FRU; for FRUs without customer data, fruadm prints only the container's path.
Only a privileged user can create or update data in containers. The privileges required to perform these write operations are hardware
dependent. Typically, a default system configuration restricts write operations to the superuser or to the platform-administrator user.
OPTIONS
The following options are supported:
-l List the system's frutree paths.
-r Recursively display or update the data for all containers rooted at the argument path.
OPERANDS
The following operands are supported:
path A full or partial system frutree path for or under which to print or set the customer data. The first field of each
line of output of fruadm -l gives the valid full frutree paths for the system.
Paths can include shell meta-characters; such paths should be quoted appropriately for the user's shell. For par-
tial paths, the first matching full path is selected for display or update. Without the -r option, the path must be
that of a container; with the -r option, all containers (if any) under path will be selected.
text Up to 80 characters of text set as the customer data. If the text contains white space or shell metacharacters, it
should be quoted appropriately for the user's shell.
EXAMPLES
Example 1: Displaying All Customer Data
The following example prints all customer data available from FRUs on the system. For containers with no customer data, only the contain-
ers' paths will be listed.
example% fruadm
Example 2: Displaying Customer Data For a Single FRU
The following command prints the customer data, if present, for the specified FRU:
example% fruadm /frutree/chassis/system-board
Example 3: Displaying Customer Data For a Single FRU
The following command prints the customer data, if present, for the first mem-module found:
example% fruadm mem-module
Example 4: Setting Customer Data
The following example sets the customer data for a FRU:
example# fruadm system-board 'Asset Tag 123456'
Example 5: Setting Customer Data
The following command sets the customer data for all FRUs under chassis:
example# fruadm -r /frutree/chassis "Property of XYZ, Inc."
EXIT STATUS
The following exit values are returned:
0 Successful completion.
>0 An error occurred.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Availability |SUNWfruip.u |
+-----------------------------+-----------------------------+
|Interface Stability |Unstable |
+-----------------------------+-----------------------------+
SEE ALSO
prtfru(1M), attributes(5)
SunOS 5.10 22 Feb 2002 fruadm(1M)