Re: USB and SD performance issue

[Koen Kooi <k.kooi@xxxxxxxxxxxxxxxxxx>]

Op 3 feb 2009, om 12:37 heeft Gadiyar, Anand het volgende geschreven:

> > -----Original Message-----
> > From: linux-omap-owner@xxxxxxxxxxxxxxx
> > [mailto:linux-omap-owner@xxxxxxxxxxxxxxx] On Behalf Of Koen Kooi
> > Sent: Tuesday, February 03, 2009 5:05 PM
> > To: Remith Ravi
> > Cc: linux-omap@xxxxxxxxxxxxxxx
> > Subject: Re: USB and SD performance issue
> >
> >
> > Op 3 feb 2009, om 12:16 heeft Remith Ravi het volgende geschreven:
> >
> > > Hello,
> > >
> > > Recently I have done a performance comparison of OMAP3 'USB
> > OTG Host'
> > > and 'SD' drivers on different Linux Kernels.
> > > The performance of latest git kernel is less comparing to
> > 2.6.22 TI
> > > kernel.
> > > Could some one please explain me what cause this performance
> > > difference?
> > >
> > > The performance is calculated by doing data transfer between RAM and
> > > the storage device (using 'time' command).
> > >
> > > The performance details are given below.
> > >
> > > 1) 2.6.29-rc2 kernel
> > > USB OTG (Host)         Read (4.2 MB/s)		Write
> > (2.6 MB/s)	
> > > SD Card                     Read (3.88 MB/s)		
> > Write (3.1 MB/s)
> > > 2) 2.6.28 kernel
> > > USB OTG (Host)         error		                error	
> > > SD Card                     Read  (4.2 MB/s)		
> > Write (3.27 MB/s)
> > > 3) 2.6.22 TI kernel
> > > USB OTG (Host)         Read (5.4MB/s)		Write
> > (6.14MB/s)	
> > > SD Card                      Read (6.7MB/s)		Write (6.43MB/s)
> >
> > I get this with 2.6.28:
> >
> > root@omap3evm:~# hdparm -t /dev/mmcblk0
> > /dev/mmcblk0:
> >  Timing buffered disk reads:   42 MB in  3.10 seconds =  13.53 MB/sec
> >
> > root@beagleboard:~# hdparm -t /dev/mmcblk0
> > /dev/mmcblk0:
> >  Timing buffered disk reads:   44 MB in  3.13 seconds =  14.04 MB/sec
> >
> > regards,
> >
> > Koen
>
> What does `hdparm -tT /dev/mmcblk0` give?

root@beagleboard:~# hdparm -tT /dev/mmcblk0
/dev/mmcblk0:
 Timing cached reads:   240 MB in  2.01 seconds = 119.32 MB/sec
 Timing buffered disk reads:   42 MB in  3.01 seconds =  13.97 MB/sec

root@omap3evm:~# hdparm -tT /dev/mmcblk0
/dev/mmcblk0:
 Timing cached reads:   300 MB in  2.00 seconds = 149.83 MB/sec
 Timing buffered disk reads:   42 MB in  3.17 seconds =  13.23 MB/sec

Which is misleading, since -T tests the bandwidth or your RAM, which  
in my case is limited since both machines are displaying a stream from  
a webcam attached to USB in X11, so the overlays and framebuffers are  
stealing a large part of the bw. Killing the screensaver on the EVM  
gave me 35MB/s 'back' :)

regards,

Koen


> - Anand

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