What are Page Faults? Only those parts of a program and data that are currently in active use need to be held in physical RAM. Other parts are then held in a swap file (as it's called in Windows 95/98/ME: Win386.swp) or page file (in Windows NT versions including Windows 2000 and XP: pagefile.sys). When a program tries to access some address that is not currently in physical RAM, it generates an interrupt, called a Page Fault. This asks the system to retrieve the 4 KB page containing the address from the page file (or in the case of code possibly from the original program file). This - a valid page fault - normally happens quite invisibly. Sometimes, through program or hardware error, the page is not there either. The system then has an 'Invalid Page Fault' error. This will be a fatal error if detected in a program: if it is seen within the system itself (perhaps because a program sent it a bad request to do something), it may manifest itself as a 'blue screen' failure with a STOP code: consult the page on STOP Messages on this site.
If there is pressure on space in RAM, then parts of code and data that are not currently needed can be 'paged out' in order to make room - the page file can thus be seen as an overflow area to make the RAM behave as if it were larger than it is. -Tim ---- Integrated Technical Services -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Peter G. Viscarola Sent: Monday, March 26, 2007 8:05 PM To: FlexRadio@flex-radio.biz Subject: Re: [Flexradio] Help! > >this page fault thing really has me curious. > Me too. Don't forget that there are "hard" and "soft" page faults in Windows. Only "hard" page faults result in the system going to disk -- "soft" page faults result in an already in-memory page being reclaimed from the transition list. Hard faults are costly, soft faults are no big deal. On a system with lots of free physical memory, Windows will allow a program to greatly exceed its working set quota. Only in the presence of memory pressure will the working set be "trimmed" and pages exceeding the process working set quota freed (by moving them to the transition list, where they're eventually moved to disk). There are many reasons you might see high numbers of page faults aside from the working set quota being enforced: Initial module load (as somebody mentioned already, a process "faults in" its pages from disk when it's first executed), memory mapped I/O, and the process allocating new (demand zero) pages. Anyone know if PowerSDR is doing either of these last two (regularly)? If PowerSDR is just "sitting there" and demodulating received signals on a system with lots of memory to spare, and it's continuously page faulting at the rate of many hundreds or a thousand per second or more, then it sounds like it could use some process tuning. de Peter K1PGV _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com/ FlexRadio Knowledge Base: http://kb.flex-radio.com/ _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com/ FlexRadio Knowledge Base: http://kb.flex-radio.com/
