Count clock cycles windows

The number and kind of performance events is very specific to the machine micro- architecture. In every day practice, we need to consult the technical reference manual for the specific microprocessor in the test platform. However, a more detailed and nuanced understanding of a specific performance event may be necessary. Contemporary microprocessors use many tricks and techniques to wring good performance out of a localized sequence of instructions in a program:.

These techniques involve complicated hardware behavior and conditions and sometimes result in highly nuanced performance events. PERF defines a set of common, symbolic hardware performance events. See the following table. These performance events are the ones that are most commonly used in practice. PERF can display a list of the available software and hardware performance events. Just enter the command:. You may also specify an event using its raw identifier. Raw event identifiers let you measure performance events that do not have a PERF symbolic name.

ARMv7, for example, does not separate cache accesses by load and store operations. You are likely to find similar compromises on other processor implementations, too. Each processor core has a set of hardware performance counters which count performance events. PERF takes care of the grungy set-up work for you. However, you need to be aware of certain processor-specific limitations such as the number of available counters and event assignment restrictions.

Any ARMv7 performance event can be assigned to any of the four performance counters. Other processors may have a different number of performance counters and certain performance counters may be restricted to one or more specific performance events.

Generally, you need to consult the appropriate processor reference manual for this information. This article part 2 concentrates on counting mode. Part 3 deals with sampling mode. Simple event counting is initiated using the perf stat command. Event sampling is handled using the perf record and perf report commands. Counting mode is very low overhead since the hardware counters do not put any additional load on the CPU. Sampling mode imposes additional overhead.

Although counting mode is low overhead, you can only measure events for the application as a whole. Overhead is higher for sampling mode, but you can isolate performance events and issues to specific regions of code e. Hardware performance counters ae fixed length registers. The Cortex-A7 performance counters are 32 bits in length.

Microprocessors are high speed and a program can easily cause a counter overflow. Simply enter a perf stat command specifying both the events to count and the application program to run:. In this example command, PERF measures CPU clock cycles and retired instructions while running the naive matrix multiplication program. Once the application program naive completes, PERF reports the number of occurences of each performance event:.

I recommend putting your PERF commands into a script so that you can easily re-run performance experiments. Program performance tuning is usually performed after bugs and other kinks have been fixed.

Tuning is an iterative process involving trial and error, and you should plan to run and re-run experiments many times. In the preceding example, PERF measured over one billion instructions and roughly 2.

How accurate are these measurements? I disassembled and analyzed the nested loops that perform matrix multiplication. Cool, Simple to use Timer as well as a great geeky Countdown clock. Know exactly how many days, hours, minutes or even seconds left until that special date or time. Stay informed about special deals, the latest products, events, and more from Microsoft Store.

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Show More. After the basic process output comes a list of the threads in the process. Other commands that display process information include! Process and thread security structures are described in Chapter 6. Windows Internals, 5th Edition. Windows Internals, Part 2, 6th Edition. Windows 7 Inside Out, Deluxe Edition.

Sign in. Your cart. Page 1 of 9 Next. In this chapter from Windows Internals, 5th Edition , learn the data structures and algorithms that deal with processes, threads, and jobs in the Windows operating system.

The first section focuses on the internal structures that make up a process. The second section outlines the steps involved in creating a process and its initial thread.

The internals of threads and thread scheduling are then described. The chapter concludes with a description of the job object. Figure Data structures associated with processes and threads. Structure of an executive process block. Structure of the executive process block. Fields of the process environment block. Image: windbg. Initialized: Yes Ldr. InInitializationOrderModuleList: c InLoadOrderModuleList: bb8. Learn more. How to count clock cycles at -O3 using Code::Blocks Ask Question.

Asked 5 years ago. Active 5 years ago. Viewed times. I use the following commands for compiling mingwgcc. Improve this question. Yes, I will update the question in few minutes. I'm calling rdtsc and rdtscp twice but actually it's recommended to call them thrice in the white paper of G. Paoloni at intel. Add a comment. Active Oldest Votes.