What is Hard Faults in XPerf

Question

I'm trying to profile a system with XPerf. And see that performance problems occurs when there is activity in HardFaults !

But what I cant figure out and find in google what are these Hard Faults that xperf shows. What are they related to? What do they indicate? Is there any universal remedy for such situations? Hard faults table

Answer 1

Indeed. "First of all, a "hard fault" was previously called a "page fault" in earlier versions of Windows. Perhaps page faults were more easily understood from the name, too. A hard fault happens when the address in memory of part of a program is no longer in main memory, but has been instead swapped out to the paging file, making the system go looking for it on the hard disk. When this happens a lot, it causes slowdowns and increased hard disk activity. When it happens an awful lot, the possibility of hard disk thrashing arises. That's when a program stops responding, but the hard drive continues to run for an extended period. This has historically been referred to as "getting into the page file."

Here is the article. http://www.brighthub.com/computing/windows-platform/articles/52249.aspx

But be carefull with following suggestions of this article, because it is not quite correct to do so: http://player.microsoftpdc.com/Session/1689962d-dea2-48bd-80d8-96e954fa5329 http://player.microsoftpdc.com/Session/1c97b279-d7e3-4a3e-9a76-0dac23dfddb5

Answer 2

A hard fault is when a the request process private page or file backed page is not in RAM. Hard faults occur for allocations that have been paged out, but also accesses to data file and executable images.

The type of page will determine where the data data will be read from. Most hard faults are not for data from teh page file, but for data files (your word doc, for example).

Answer 3

Vaguely I remember a hard fault is when the requested virtual memory block is not in memory anymore and needs to be paged-in from the swapfile.