[U-Boot] Testing Data Cache for armv7 (beagleboard)

[Wolfgang Denk]

Dear chris c,

In message <AANLkTi=usuEyf4YuUVWrrLu80bMRFpRF+BThEix2bFNg at mail.gmail.com> you wrote:
>
> I was comparing time just by timing it manually.  How did you instrument
> u-boot to display the time?

That's no instrumentation of U-Boot, but just timestamping the output
on the serial console. See for example
ftp://ftp.denx.de/pub/tools/time_log

> As for the small versus large file, I did the same test for 1MB of data
> using nand read and saw a x4 performance advantage.  I also did a test on
> mmc with 100 MB file and saw no performance increase.  Looks like file size
> doesn't matter.
> 
> So does that mean that MMC file loading will not benefit from dcache
> enabled?  Can anybody explain this?

It depends on where the time is actually spent. If you have a slow
(say, bit-banging) MMC driver and a low-performance CPU then the
transfer from MMC might simply not depend as much on caches. It is
wrong to check just a simple use case. Try a number of different
operations, like umcompressing a large image in RAM or from NOR to
RAM, or downloading over the net, or ...

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
"Remember, Information is not knowledge;  Knowledge  is  not  Wisdom;
Wisdom is not truth; Truth is not beauty; Beauty is not love; Love is
not music; Music is the best."                          - Frank Zappa