Desired timeslice in seconds1/19/2024 There are really only two automated methods. The OS needs to use some other method for obtaining an initial time and date. When the computer is turned off, obviously system software cannot keep an internal clock updated using a timer. (for file system accesses, especially), and the format used often isn't what the OS wants. Depending on the reference used, this method may only be accurate to 1 second, it may be slow, it may be needed often It is also possible not to use a timer to update the system clock at all, and only use an "accurate" external reference when the system tries toĪccess the system clock. However, some of these timers are only accurate to within a handful of seconds a day, so it may be desirable to benchmark the systemĬlock to a reference, periodically, even while the system is running. Know how often the chosen timer ticks during one second, and keep a counter - or the system clock may be designed to tick at It takes very little additional code in the driver to also use that timer to update the system clock. Using at least one of these timers is probably necessary to control and generate scheduler timeslice ticks. These timers may produce an interrupt (or may even be polled) at regular intervals to inform the OS of the passage of time. On an x86 system, there are two to four timers available: the PIT, the RTC, the TSC, or the local APIC (older systems may not have a TSC During operation, a typical OS will use a local hardware timer to drive its own internal time keeping code - often called the "system clock".
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