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Full Discussion: kernel:how to modify and read the tick rate:HZ
Operating Systems Linux kernel:how to modify and read the tick rate:HZ Post 302156391 by amit4g on Tuesday 8th of January 2008 04:20:17 AM
Old 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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LEARN ABOUT CENTOS

zone2ldap

zone2ldap(1)						      General Commands Manual						      zone2ldap(1)

NAME

       zone2ldap /- Load BIND 9 Zone files into LDAP Directory

SYNOPSIS

       zone2ldap  [-D Bind DN] [-w Bind Password] [-b Base DN] [-z Zone] [-f Zone File ] [-h Ldap Host] [-cd] [-v]

DESCRIPTION

       zone2ldap  will parse a complete BIND 9 format DNS zone file, and load the contents into an LDAP directory, for use with the LDAP sdb back-
       end.

       If the zone already exists, zone2ldap will exit succesfully. If the zone does not exists, or partially exists, zone2ldap  will  attempt	to
       add all/missing zone data.

   Options
       -b     LDAP  Base DN. LDAP systems require a "base dn", which is generally considered the LDAP Directory root.  If the zone you are loading
	      is different from the base, then you will need to tell zone2ldap what your LDAP base is.

       -v     Print version information, and immediatly exit.

       -f     Zone file.  Bind 9.1 compatible zone file, from which zone information will be read.

       -d     Dump debug information to standard out.

       -w     LDAP Bind password, corresponding the the value of "-b".

       -h     LDAP Directory host. This is the hostname of the LDAP system you wish to store zone information on.  An LDAP server should  be  lis-
	      tening on port 389 of the target system. This may be ommited, and will default to "localhost".

       -c     This will create the zone portion of the DN you are importing. For instance, if you are creating a domain.com zone, zone2ldap should
	      first create "dc=domain,dc=com".	This is useful if you are creating multiple domains.

       -z     This is the name of the zone specified in the SOA record.

EXAMPLES

       Following are brief examples of how to import a zone file into your LDAP DIT.

   Loading zone domain.com, with an LDAP Base DN of dc=domain,dc=com
       zone2ldap -D dc=root -w secret -h localhost -z domain.com -f domain.com.zone

       This will add Resource Records into an ALREADY EXISTING dc=domain,dc=com. The final SOA DN in this case, will be dc=@,dc=domain,dc=com

   Loading customer.com, if your LDAP Base DN is dc=provider,dc=net.
       zone2ldap -D dc=root -w secret -h localhost -z customer.com -b dc=provider,dc=net -f customer.com.zone -c

       This will create dc=customer,dc=com under dc=provider,dc=net, and add all necessary Resource Records. The final root DN to the SOA will	be
       dc=@,dc=customer,dc=com,dc=provider,dc=net.

SEE ALSO

       named(8) ldap(3) http://www.venaas.no/ldap/bind-sdb/

BUGS

       Send all bug reports to Jeff McNeil <jeff@snapcase.g-rock.net>

AUTHOR

       Jeff McNeil <jeff@snapcase.g-rock.net>

								   8 March 2001 						      zone2ldap(1)
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