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

[VAXman- at SendSpamHere.ORG]

In article <ebqdndZbSPxxrPHRnZ2dnUVZ_umdnZ2d at giganews.com>, "Richard B. Gilbert" <rgilbert88 at comcast.net> writes:
>Bob Koehler wrote:
>> 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.
>> 
>
>Usually, alignment errors have to be forced or something like that.  The 
>compilers will align everything properly unless the programmer 
>deliberately creates a data structure with non-aligned components. 

It's far easier than you think!!!


>There may, occasionally, be good reason to do something like this but I 
>can't think of one and I think best practice is to avoid it like the plague!

I can.

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VAXman- A Bored Certified VMS Kernel Mode Hacker    VAXman(at)TMESIS(dot)ORG

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