🚀 go-pugleaf

Mwp,

> I kinda understand what PageFaults are, 

A page fault occurs when the CPU tries to access an address which is not 
backed by (IOW:present in) physical RAM. In response to a page fault the OS 
will attempt to allocate a page of RAM to back the address.

Depending on why the page fault occurred this can quite a quick process (as
when simply completing a lazy allocation) or slow (as when reading data back
from the swap file - esp. if something else has to be thrown out). It's 
actually quite a fascinating aspect of OS design (well I think so) and 
there's quite a lot of documentation on the web.


In Builder terms it could be one of:
  * You are reading/writing to an area of the heap that has been swapped out
  to disk.
  * You are reading/writing to an area of the heap that you have never
  accessed before and the OS is now scrambling to provide storage for you. The 
  last I heard Windows NT and higher use a lazy allocation strategy so storage
  isn't actually allocated until you make use of it.

You'll also get page faults when writing to a copy-on-write page but this is
probably very rare for a Builder program.

> but what i cant understand is why my BCB5 app creates so many.
> Its creating about 1000 a second.

If you are allocating a large amount of memory in small chunks this could 
happen. *This probably doesn't matter as long as the allocation isn't a runaway 
situation since it should calm down after a while.*

It could also happen if you are allocating a small amount of memory but mixing
your allocations such that the Heap Manager was unable to satisfy your requests
from its free list. This is a problem that Borland's Heap Managers (Delphi and 
C++) have suffered from for as long as I know. Typically a mix of large/small
allocations will have this effect even if they are being continually deallocated. 
IOW sometimes even though the instantaneous allocated total is low the
Heap Manager may still be having to request memory from Windows. *This can be
a problem as it affects performance and could eventually lead to an out of
resources message*.

It could also happen if you have allocated a lot of memory and are jumping
around it a lot (a large hash list for instance). This is especially likely
if your machine has small amounts of RAM or is running a lot of other memory
hungry applications. *This is annoying but aside from the performance drop
is unlikely to cause a crash*.

--
Andrue Cope
[Bicester, UK]