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A Linux boot log showing the usage of TSC as system clocksource. The Time Stamp Counter (TSC) is a 64-bit register present on all x86 processors since the Pentium. It counts the number of CPU cycles since its reset. The instruction RDTSC returns the TSC in EDX:EAX. In x86-64 mode, RDTSC also clears the upper 32 bits of RAX and RDX.
The perf subsystem of Linux kernels from 2.6.37 up to 3.8.8 and RHEL6 kernel 2.6.32 contained a security vulnerability (CVE-2013-2094), which was exploited to gain root privileges by a local user. [ 17 ] [ 18 ] The problem was due to an incorrect type being used (32-bit int instead of 64-bit) in the event_id verification code path.
The number of available hardware counters in a processor is limited while each CPU model might have a lot of different events that a developer might like to measure. Each counter can be programmed with the index of an event type to be monitored, like a L1 cache miss or a branch misprediction.
nice is a program found on Unix and Unix-like operating systems such as Linux. It directly maps to a kernel call of the same name. nice is used to invoke a utility or shell script with a particular CPU priority, thus giving the process more or less CPU time than other processes. A niceness of -20 is the lowest niceness, or highest priority.
An idle computer has a load number of 0 (the idle process is not counted). Each process using or waiting for CPU (the ready queue or run queue) increments the load number by 1. Each process that terminates decrements it by 1. Most UNIX systems count only processes in the running (on CPU) or runnable (waiting for CPU) states.
The nearest power-of-2 integer that is not smaller than this value is the number of unique initial APIC IDs reserved for addressing different logical processors in a physical package. [a] Former use: Number of logical processors per physical processor; two for the Pentium 4 processor with Hyper-Threading Technology. [47]
It is a multi-purpose benchmark that features tests for CPU, memory, I/O, and database performance testing. [3] It is a basic command line utility that offers a direct way to benchmark computer hardware. It now comes packaged in most major Linux distribution repositories such as Debian, Ubuntu, CentOS and Arch Linux. [4]
BogoMips (from "bogus" and MIPS) is a crude measurement of CPU speed made by the Linux kernel when it boots to calibrate an internal busy-loop. [1] An often-quoted definition of the term is "the number of million times per second a processor can do absolutely nothing".