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

[Main, Kerry]

> -----Original Message-----
> From: info-vax-bounces at rbnsn.com [mailto:info-vax-bounces at rbnsn.com]
> On Behalf Of Bob Koehler
> Sent: August-18-10 9:11 AM
> To: info-vax at rbnsn.com
> Subject: Re: [Info-vax] SAMBA really sloooow on OVMS Integrity. Any
> Ideas????
> 
> 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.
> 
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Good tech journal alignment article from Guy Peleg:
http://h71000.www7.hp.com/openvms/journal/v9/alignment_faults.pdf 

And alignment faults are not specific to OpenVMS - here is Wintel article
on same topic:

http://msdn.microsoft.com/en-us/library/aa290049(VS.71).aspx


Regards,

Kerry Main
Senior Consultant
HP Services Canada
Voice: 613-797-4937
Fax: 613-591-4477
kerryDOTmainAThpDOTcom
(remove the DOT's and AT)

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