![]() ![]() The performance of applications will suffer when there is insufficient RAM and excessive hard page faults occur. Once the copy has completed successfully, the OS allows the program thread to continue on. The OS then locates a copy of the desired page on the page file, and copies the page from disk into a free page in RAM. ![]() There is an Interrupt Service Routine that gains control at this point and determines that the address is valid, but that the page is not resident. The instruction that referenced the page fails and generates an addressing exception that generates an interrupt. When a thread attempts to reference a nonresident memory page, a hardware interrupt occurs that halts the executing program. What happens when a page fault occurs is that the thread that experienced the page fault is put into a Wait state while the operating system finds the specific page on disk and restores it to physical memory. A page fault occurs when a program requests an address on a page that is not in the current set of memory resident pages. (high count indicates working set is too large for memory to handle - could be a mix of hard and soft faults). Memory: Page Faults /sec - measures the working set.To look for excessive paging, use Task Manager and add the column: Page Faults and PF Delta for current activity. If both are high, these are hard faults (working set replacement). If the Pages/sec are high, but the % Usage is low, these are soft faults (cached memory). This counter needs to be used in conjunction with Paging File: %Usage. Memory: Pages/sec – measures the number of pages per second that are paged out of RAM to Virtual Memory (HDD)or ‘hard faults’ OR the reading of memory-mapping for cached memory or ‘soft faults’ (systems with a lot of memory). ![]()
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