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POHow do I ensure my program runs from beginning to end without interruption?
 

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  1. POHow do I ensure my program runs from beginning to end without interruption?
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    <p>I'm attempting to time code using RDTSC (no other profiling software I've tried is able to time to the resolution I need) on Ubuntu 8.10. However, I keep getting outliers from task switches and interrupts firing, which are causing my statistics to be invalid.</p> <p>Considering my program runs in a matter of milliseconds, is it possible to disable all interrupts (which would inherently switch off task switches) in my environment? Or do I need to go to an OS which allows me more power? Would I be better off using my own OS kernel to perform this timing code? I am attempting to prove an algorithm's best/worst case performance, so it must be totally solid with timing.</p> <p>The relevant code I'm using currently is:</p> <pre><code>inline uint64_t rdtsc() { uint64_t ret; asm volatile("rdtsc" : "=A" (ret)); return ret; } void test(int readable_out, uint32_t start, uint32_t end, uint32_t (*fn)(uint32_t, uint32_t)) { int i; for(i = 0; i &lt;= 100; i++) { uint64_t clock1 = rdtsc(); uint32_t ans = fn(start, end); uint64_t clock2 = rdtsc(); uint64_t diff = clock2 - clock1; if(readable_out) printf("[%3d]\t\t%u [%llu]\n", i, ans, diff); else printf("%llu\n", diff); } } </code></pre> <p>Extra points to those who notice I'm not properly handling overflow conditions in this code. At this stage I'm just trying to get a consistent output without sudden jumps due to my program losing the timeslice.</p> <p>The nice value for my program is -20.</p> <p>So to recap, is it possible for me to run this code without interruption from the OS? Or am I going to need to run it on bare hardware in ring0, so I can disable IRQs and scheduling? Thanks in advance!</p>
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    1. USMatthew Iselin
    1. USMatthew Iselin
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      1. USJoseph Garvin
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    1. COHave you tried OProfile: http://oprofile.sourceforge.net/news/
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      1. USKarl Voigtland
 

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