[syslinux] memdisk speed diagnostics?

[Gene Cumm]

On Apr 4, 2012 7:12 PM, "Bernd Blaauw" <bblaauw at home.nl> wrote:
>
> Would it be a usefull addition to memdisk's "pause" parameter if it
showed the loading speed for the specified disk image file?

To my knowledge, adding the "pause" parameter doesn't impact the output
except for the prompt.

> The idea is to verify if a device is really loading an operating system's
data at the intended device/controller/interface/bus (etc) speed. My own
system has a habit of setting usb2.0 interface to 1.1-speeds for example.

This is extremely common.  I believe I even have a system that went from no
USB boot to 12Mbps max to 480 Mbps max in its revisions.

I wrote cptime.c32 for a similar purpose.  It will time how long it takes
to copy (dump) a file with a bunch of available options (chunk size and max
length for starters).

> With (hopefully) bootable USB3.0 interfaces coming soon, a MEMDISK
combined with a sufficient sized disk image (say 170MB Parted Magic
cd-image file) would show loading speeds between 60MB and 500MB if a
suitable device (USB3.0 Flash Drive or USB3.0-connected SSD) is used.
>
> Unfortunately I'd have no idea how to take compression (gzip/zip) into
account, it can alter numbers significantly.
>
> perhaps something like this:
> "loaded/copied/read nnnn MB in tttt seconds (average speed nn MB/s)"
>
> or
>
> "done reading nnnn MB in tttt seconds (average speed nn MB/s)"
> "decompressed to mmmm MB in uuuu seconds (average speed mm MB/s)"

Depending on the level of compression, compressibility of data, cpu
speed/design and other factors, you could see decompression impact ranging
from negligible to the primary time consumer.

--Gene