[Info-vax] SAMBA really sloooow on OVMS Integrity. Any Ideas????

[Bob Koehler]

In article <b10eda82-8d64-428b-805b-71ccd0ca40e9 at x20g2000pro.googlegroups.com>, Len Whitwer <len at psds.com> writes:
> 
> We build from Samba download on HP's site. (What is an alignment fault
> and how can I tell if we are getting them?)

   An alignment fault happens when you access an address that is not
   an even multiple of the data size.  When a compiler can see that
   you're going to do this, it should generate the necessary code
   to access the surrounding larger data size and then strip off the
   desired data.  When a compiler can't see this, or if the compiler
   just isn't that robust, the instruction that accesses the data will
   cause an alignment fault, which will get trapped, the data fetch
   will be fixed up, and then the fault dismissed.  This takes longer
   than just fixing up the access in the first place.

   Sometimes code must interface to external data streams that are
   defined in poorly aligned manners.  Internal data stores should
   always be allowed to be aligned (compilers like to do that for you).

   The best way to access a poorly alined external data stream is to
   grab the whole thing, then code the movement from an unaligned to
   an aligned copy (or back) in such a manner as not to create alignment
   faults.

   There are tools in VMS to monitor alignment faults, but I've never
   used them so someone else will have to chime in here.