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Top Forums Programming How can I get a processor's CPU Percentage? Post 8672 by Perderabo on Tuesday 16th of October 2001 11:24:11 AM
Old 10-16-2001
Kernels always have some code built in to gather statistics. In the case of cpus, several times a second a clock routine fires off and increments one element of a structure. The structure will have counters for idle, user, system, and so on.

In the old days, you could get the structure if you knew its name. You would run nlist(3) on the kernel's symbol table to get the address of the structure. Then you opened /dev/kmem. did a seek to the address and read the structure. The c definations of the structures were usually in /usr/include. This still can be made to work on hp-ux, but the required information is no longer supplied in /usr/include. Skilled gurus can reverse-engineer it, but it's difficult. Vic Able has done this to get lsof to work on recent versions of HP-UX, a feat that very few could match.

New system calls like pstat are the way of the future. And pstat works well enough. Why do you want an alternative?
 

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kvm_nlist(3KVM)                                             Kernel VM Library Functions                                            kvm_nlist(3KVM)

NAME
kvm_nlist - get entries from kernel symbol table SYNOPSIS
cc [ flag... ] file... -lkvm [ library...] #include <kvm.h> #include <nlist.h> int kvm_nlist(kvm_t *kd, struct nlist *nl); DESCRIPTION
The kvm_nlist() function examines the symbol table from the kernel image identified by kd (see kvm_open(3KVM)) and selectively extracts a list of values and puts them in the array of nlist structures pointed to by nl. The name list pointed to by nl consists of an array of structures containing names, types and values. The n_name field of each such structure is taken to be a pointer to a character string rep- resenting a symbol name. The list is terminated by an entry with a null pointer (or a pointer to a null string) in the n_name field. For each entry in nl, if the named symbol is present in the kernel symbol table, its value and type are placed in the n_value and n_type fields. If a symbol cannot be located, the corresponding n_type field of nl is set to 0. RETURN VALUES
The kvm_nlist() functions returns the value of nlist(3UCB) or nlist(3ELF), depending on the library used. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Stable | +-----------------------------+-----------------------------+ |MT-Level |Unsafe | +-----------------------------+-----------------------------+ SEE ALSO
kvm_open(3KVM), kvm_kread(3KVM), nlist(3ELF), nlist(3UCB), attributes(5) NOTES
Although the libkvm API is Stable, the symbol names and data values that can be accessed through this set of interfaces are Private and are subject to ongoing change. SunOS 5.10 2 May 2002 kvm_nlist(3KVM)
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