# minor page faults question

## zzaappp

I have a box with 32gigs of RAM and 8 cores (two dual quads).  The total application memory space (including shared memory for IPC) requires less than 15 gigs.  Since we have plenty of memory and need the performance I have been running without swap space for over a year.  Last week I was poking around and noticed that our applications are causing minor page faults.    Since our apps are single threaded, trivial things, and since swap is off, how can they still be causing minor page faults?  

Btw, no major page faults at all.  That one makes more sense to me.

Many thanks!

-z

----------

## BradN

This could be due to programs using memory mapped files.  When a program is run, linux memory maps the binary and all the libraries it needs, but they're not actually loaded into RAM until the first time they're used.  In addition, programs can memory map files themselves.

I'm not an expert on different types of page faults, but from my understanding, running a swapless system doesn't entirely eliminate page faults for this reason, however I don't think they should be continuously occurring in the same process as long as there's enough RAM to keep the working set (plus mmap'ed data) in memory.

Some architectures have a separate fault of sorts to tell the operating system to load different MMU mappings into the hardware cache, but I don't know if this is involved here.

----------

