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

[chris c]

Heiko,

I was comparing time just by timing it manually.  How did you instrument
u-boot to display the time?

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?

Thanks.

On Thu, Oct 7, 2010 at 1:14 AM, Heiko Schocher <hs at denx.de> wrote:

> Hello Chris,
>
> chris chriss wrote:
> > I'm trying to test the cache on my beagle with a snapshot from the git
> tree
> > today.  I tried it out by loading a file from the mmc with dcache off and
> > then dcache on.  I didn't see any difference in speed.  After reading
> this
> > commit (http://git.denx.de/?p=u-boot.git;a=commit;h=95c6f6d), I expected
> to
> > see a performance improvement.
>
> Here a log which actual reloacte code from Albert Aribaud and
> my fix patch for the beagle on the beagle board:
>
>  170.880 U-Boot 2010.09-00102-g456a0da-dirty (Oct 05 2010 - 14:41:10)
>  170.880
>  170.920 OMAP3530-GP ES3.0, CPU-OPP2, L3-165MHz, Max CPU Clock 600 mHz
>  170.920 OMAP3 Beagle board + LPDDR/NAND
>  170.960 I2C:   ready
>  170.960 DRAM:  128 MiB
>  171.000 NAND:  256 MiB
>  174.000 In:    serial
>  174.000 Out:   serial
>  174.000 Err:   serial
>  174.000 Beagle Rev C1/C2/C3
>  174.360 Die ID #00b000030000000004013f8a1700900c
>  175.200 Hit any key to stop autoboot:  0
>  175.440 OMAP3 beagleboard.org #
>  178.280 OMAP3 beagleboard.org # ica off
>  178.280 Instruction Cache is OFF
>  180.480 OMAP3 beagleboard.org # dca off
>  180.480 Data (writethrough) Cache is OFF
>  183.520 OMAP3 beagleboard.org # echo start ; nand read 80800000 0 7000000
> ; echo stop
>   0.000 start
>   0.000
>   0.000 NAND read: device 0 offset 0x0, size 0x7000000
>  114.040 NAND read from offset 0 failed -74
>  114.040  117440512 bytes read: ERROR
>  114.040 stop
>  135.880 OMAP3 beagleboard.org # ica on
>  135.880 Instruction Cache is ON
>  138.280 OMAP3 beagleboard.org # echo start ; nand read 80800000 0 7000000
> ; echo stop
>   0.000 start
>   0.000
>   0.000 NAND read: device 0 offset 0x0, size 0x7000000
>  95.120 NAND read from offset 0 failed -74
>  95.120  117440512 bytes read: ERROR
>  95.120 stop
>  160.880 OMAP3 beagleboard.org # dca on
>  160.880 Data (writethrough) Cache is ON
>  164.600 OMAP3 beagleboard.org # ica on
>  164.600 Instruction Cache is ON
>  166.080 OMAP3 beagleboard.org # echo start ; nand read 80800000 0 7000000
> ; echo stop
>   0.000 start
>   0.000
>   0.000 NAND read: device 0 offset 0x0, size 0x7000000
>  26.680 NAND read from offset 0 failed -74
>  26.680  117440512 bytes read: ERROR
>  26.680 stop
>
> > This is a capture of how I tested it...
> >
> > <capture>
> >
> > OMAP3 beagleboard.org # mmc init 1
> > mmc1 is available
> > OMAP3 beagleboard.org # dcache
> > Data (writethrough) Cache is OFF
> > OMAP3 beagleboard.org # fatload mmc 0:1 0x80000000 uImage.bin
> > reading uImage.bin
> >
> > 3852836 bytes read
> > OMAP3 beagleboard.org # dcache on
> > Data (writethrough) Cache is ON
> > OMAP3 beagleboard.org # fatload mmc 0:1 0x80000000 uImage.bin
> > reading uImage.bin
> >
> > 3852836 bytes read
> > OMAP3 beagleboard.org #
> >
> > </capture>
>
> How did you measured the time between start an end?
>
> Maybe uImage.bin is a little bit to small for seeing some
> effect?
>
> bye,
> Heiko
>