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POWhy would a device driver cause page faults?
 

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  1. POWhy would a device driver cause page faults?
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    <p>I have a Windows console application that uses a parallel IO card for high speed data transmission. (General Standards <a href="http://www.generalstandards.com/view-products2.php?BD_family=hpdi32alt" rel="nofollow">HPDI32ALT</a>)</p> <p>My process is running in user mode, however, I am sure somewhere behind the device's API there is some kernel mode driver activity (PCI DMA transfers, reading device status registers etc..) The working model is roughly this:</p> <ul> <li>at startup: I request a pointer to an IO buffer from API.</li> <li>in my main loop: <ul> <li>block on API waiting for room in device's buffer (low watermark)</li> <li>fill the IO buffer with transmission data</li> <li>begin transmission to device by passing it the pointer to the IO buffer (during this time the API uses DMA on PCI bus to move the data to the card)</li> <li>block on API waiting for IO to complete</li> </ul></li> </ul> <p>The application appears to be working correctly with proper data rate and sustained throughput for long periods of time, however, when I look at the process in sys internals tool process explorer I see a large number of page faults (~6k per second). I am moving ~30MB/s to the card.</p> <p>I have plenty of RAM and am reasonably sure the page faults are not disk IO related.</p> <p>Any thoughts on what could be causing the page faults? I also have a receive side to this application that is using an identical IO card in receive mode. The receive mode use of the API does not cause a large number page faults.</p> <p>Could the act of moving the IO buffer to kernel mode cause page faults?</p>
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