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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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nlist(3ELF)						       ELF Library Functions						       nlist(3ELF)

NAME
nlist - get entries from name list SYNOPSIS
cc [ flag... ] file ... -lelf [ library ... ] #include <nlist.h> int nlist(const char *filename, struct nlist *nl); DESCRIPTION
nlist() examines the name list in the executable file whose name is pointed to by filename, and selectively extracts a list of values and puts them in the array of nlist() structures pointed to by nl. The name list nl consists of an array of structures containing names of variables, types, and values. The list is terminated with a null name, that is, a null string is in the name position of the structure. Each variable name is looked up in the name list of the file. If the name is found, the type, value, storage class, and section number of the name are inserted in the other fields. The type field may be set to 0 if the file was not compiled with the -g option to cc(1B). nlist() will always return the information for an external symbol of a given name if the name exists in the file. If an external symbol does not exist, and there is more than one symbol with the specified name in the file (such as static symbols defined in separate files), the values returned will be for the last occurrence of that name in the file. If the name is not found, all fields in the structure except n_name are set to 0. This function is useful for examining the system name list kept in the file /dev/ksyms. In this way programs can obtain system addresses that are up to date. RETURN VALUES
All value entries are set to 0 if the file cannot be read or if it does not contain a valid name list. nlist() returns 0 on success, -1 on error. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Stable | +-----------------------------+-----------------------------+ |MT-Level |Safe | +-----------------------------+-----------------------------+ SEE ALSO
cc(1B), elf(3ELF), kvm_nlist(3KVM), kvm_open(3KVM), libelf(3LIB), a.out(4), attributes(5), ksyms(7D), mem(7D) SunOS 5.11 11 Jul 2001 nlist(3ELF)
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