What are Jiffies kernel?
The global variable “jiffies” holds the number of ticks that have occurred since the system booted. On boot, the kernel initializes the variable to zero, and it is incremented by one during each timer interrupt. Thus, because there are HZ timer interrupts in a second, there are HZ jiffies in a second.
What is Linux Clocksource?
The clocksource concept represents the generic API for clock sources management in the Linux kernel. Besides this, each architecture can provide a driver for the architecture-dependent real time clock, for example – CMOS/RTC – arch/x86/kernel/rtc. c for the x86 architecture.
What is HZ value in Linux kernel?
13, the HZ value is a kernel configuration parameter and can be 100, 250 (the default) or 1000, yielding a jiffies value of, respectively, 0.01, 0.004, or 0.001 seconds. Since kernel 2.6. 20, a further frequency is available: 300, a number that divides evenly for the common video frame rates (PAL, 25 HZ; NTSC, 30 HZ).
How long is a jiffy kernel?
1 ms
It is not an absolute time interval unit, since its duration depends on the clock interrupt frequency of the particular hardware platform under review. Within the Linux 2.6 operating system kernel, on the Intel i386 platform, a jiffie is 1 ms, or 1/1000th of a second. It is different on other hardware platforms.
How do you convert Jiffies to seconds?
Divide jiffies by the number you get from sysconf(_SC_CLK_TCK) to get the total number of seconds.
What are Jiffies and Hz?
What it means is that jiffies is incremented HZ times every second. If HZ = 1,000, then it is incremented 1,000 times (that is, one tick every 1/1,000 seconds).
What is the clock source for the time?
1. What is the clock source for the timers? Explanation: Timer’s clock source is the crystal that is applied to the controller.
What is KVM clock?
kvm-clock is a Linux clocksource like tsc and hpet. ( tsc is commonly used on physical machines.) The discussion at the URL below indicates that all clocksources act like time counters that are periodically read by interrupts.
What is the value of HZ?
It is measured in hertz (Hz), an international unit of measure where 1 hertz is equal to 1 cycle per second. Hertz (Hz) = One hertz is equal to one cycle per second.
What is kernel clock?
Concepts. The kernel supports two distinct clocks. The 32-bit hardware clock is a high precision counter that tracks time in unspecified units called cycles. The duration of a cycle is determined by the board hardware used by the kernel, and is typically measured in nanoseconds.
What is the use of Jiffies?
The global variable jiffies holds the number of ticks that have occurred since the system booted. On boot, the kernel initializes the variable to zero, and it is incremented by one during each timer interrupt. Thus, because there are HZ timer interrupts in a second, there are HZ jiffies in a second.