[Info-vax] OpenVMS async I/O, fast vs. slow

[Arne Vajhøj]

On 11/4/2023 1:06 PM, Craig A. Berry wrote:
> 
> On 11/4/23 6:11 AM, Johnny Billquist wrote:
> 
>> I'm not sure I have ever understood why people think memory mapped 
>> files would be faster than a QIO under VMS.
> 
> I might've missed it but I haven't seen anyone say that. It's that
> global sections are faster than mailboxes. The I/O API may be a
> consideration but is secondary to the nature of the device.

I guess that I as usual will have to plead guilty.

I wrote:

# The normal assumption regarding speed of disk IO would be that:
#
# RMS record IO ($GET and $PUT) < RMS block IO ($READ and $WRITE) <
# $QIO(W) < $IO_PERFORM(W) < memory mapped file
#
# (note that assumption and fact are spelled differently)

Arne