When would you use one utility over the other? If you are running a single application or a couple of programs, use timex. It can be used to trace the activity of a single process, a related group of processes, or the system as a whole. The par utility has the ability to trace system call and scheduling activity. In addition, the utilities display the data differently. The sar program also has options that allow sampling of a specific function such as CPU usage ( -u option) or paging ( -p option). The difference is that timex takes a sample over a single span of time, while sar takes a sample at specified time intervals. Both utilities use sadc, the sar data collector, which collects data from the operating system counters and puts it in a file in binary format. The timex and sar utilities monitor the value of the operating system counters, and thus sample system performance. You can monitor internal system activity by reading the values of these counters. Each time an operation is performed, an associated counter is incremented. The operating system has a number of counters that measure internal system activity. They provide very useful information about what is happening in the system. Three utilities you can use to monitor system performance are Here are a few of the parameters you may want to adjust are: If you have a lot of memory or your environment has special needs, you may want to adjust the size of a parameter to meet those needs. The default values for the tunable parameters are usually acceptable for most configurations for a single-user workstation environment. For mtune and master.d information, see the Tunable parameters are specified in separate configuration files in the Appendix A, “IRIX Kernel Tunable Parameters” describes all parameters, gives default values, provides suggestions on when to change each parameter, and describes problems you may encounter. This section briefly introduces some of the tunable parameters and switches. If they are set too low, they can cause excessive I/O, process aborts, or even a system crash, depending on the particular parameter. If certain system structures are too large, they waste memory space that would be used for other processes and can increase system overhead due to lengthy table searches. They set various table sizes and system thresholds to handle the expected system load. You can use sched_rr_get_interval() to get the SCHED_RR interval for a specific SCHED_RR process.Tunable parameters control characteristics of processes, files, and system activity. * Timeslices get refilled after they expire. * default timeslice is 100 msecs (used only for SCHED_RR tasks). That means the timeslice for each process is proportional to the current load and weighted by the process' priority value.įor special-purpose realtime processes which use SCHED_RR, the default timeslice is defined in the Linux kernel as RR_TIMESLICE in include/linux/sched/rt.h. This is because the Completely Fair Scheduler, the default Linux scheduler, assigns a proportion of the processor to a process rather than a fixed timeslice. Uninterrupted CPU time" that you may expect it to be. "slice" of CPU time, but preemption will be triggered only if a moreĭeserving task is available, so a "slice" is not the "max A task may have received a full (variable) Also note that CFS preemption decisions are based upon Sched_min_granularity_ns, but note that "slice" is not a fixed You can tune "slice" by adjusting sched_latency_ns and The quantum allocated for a particular process may vary:
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