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Use RDTSC instruction to measure time on x86 architecture

In x86 architecture, RDTSC instruction reads current time stamp counter from the hardware. This is a better cost measurement for a program than using GNU time. It’s overhead is low and accuracy is high. You can simply add the following function to get the current counter. 

typedef unsigned long long cycles_t;
inline cycles_t currentcycles() {
    cycles_t result;
    __asm__ __volatile__ ("rdtsc" : "=A" (result));
    return result;
}

This entry was posted on Sunday, September 24th, 2006 at 9:07 pm and is filed under Linux, Programming. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

2 Responses to “Use RDTSC instruction to measure time on x86 architecture”

  1. John Smith Says:
    January 8th, 2010 at 8:28 pm

    Sometimes exact UTC time is required. Ntp server steps in with powerful linux tools (like GPS NTP on linux)

  2. Jungwoo Ha Says:
    January 13th, 2010 at 8:29 pm

    RDTSC is using the hardware clock. It indicates # of cycles, and not the time. Cycles are better indication of the time spent in an application, because of the granularity it can measure.

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