UPGRADE YOUR BROWSER

We have detected your current browser version is not the latest one. Xilinx.com uses the latest web technologies to bring you the best online experience possible. Please upgrade to a Xilinx.com supported browser:Chrome, Firefox, Internet Explorer 11, Safari. Thank you!

cancel
Showing results for 
Search instead for 
Did you mean: 
Adventurer
Adventurer
7,099 Views
Registered: ‎03-29-2008

SD card performance using Zynq SDIO and Linux, what data rates can be expected?

The title tells most of the tale. I am wondering about benchmarks that show the performence of the SDIO in Zynq on a systme running the Xilinx Linux from the GIT server. Reference designs would be very nice.

 

Does anyone have real numbers? Good guesses?

 

 

Thanks

Nick

0 Kudos
6 Replies
Scholar austin
Scholar
7,097 Views
Registered: ‎02-27-2008

Re: SD card performance using Zynq SDIO and Linux, what data rates can be expected?

Per the documents, it says "up to 25 MB/sec."

 

 

Austin Lesea
Principal Engineer
Xilinx San Jose
0 Kudos
Scholar milosoftware
Scholar
7,077 Views
Registered: ‎10-26-2012

Re: SD card performance using Zynq SDIO and Linux, what data rates can be expected?

It's guaranteed to never exceed 25 MB/s.

 

In real life, you'll get something akin to this:

 

root@zedboard:/media/mmcblk0p2# time dd if=/dev/zero of=dummy bs=32768 count=100
00                                                                              
10000+0 records in                                                              
10000+0 records out                                                             
real    1m 18.96s                                                               
user    0m 0.03s                                                                
sys     0m 1.28s                                                                

That would be about 4 MB per second.

 

The results depend on the filesystem, CPU, SD card, and probably a bunch of other things as well. The number above is about as slow as you can get: Cheap SD card, badly configured ext4 filesystem, and the slowest Zynq in existence. A bit of tuning in filesystem will probably double the result.

 

 

0 Kudos
Scholar austin
Scholar
7,070 Views
Registered: ‎02-27-2008

Re: SD card performance using Zynq SDIO and Linux, what data rates can be expected?

m,

 

Good points! 

Austin Lesea
Principal Engineer
Xilinx San Jose
0 Kudos
Adventurer
Adventurer
7,064 Views
Registered: ‎03-29-2008

Re: SD card performance using Zynq SDIO and Linux, what data rates can be expected?

Thanks to  milosoftware. I now have a bottom 4MB/s and a max 25MB/s (Thank you Austin).  That is a start, now I need to define what “A bit of tuning” is and what sort of design setup would one make to realize this “A bit of tuning” and I am there.

 

Any more hints?  Any reference designs with “A bit of tuning” in them?

 

Thanks for everything so far, it is very useful.

 

Nick

0 Kudos
Scholar milosoftware
Scholar
7,053 Views
Registered: ‎10-26-2012

Re: SD card performance using Zynq SDIO and Linux, what data rates can be expected?

Well what are your goals. There are just too many variables to consider.

 

Fastest reading? Fastest writing? Constant minimal speed (e.g. PVR applications)?
What filesystem do you want to use? Do you want to use a filesystem at all?

What is the source of the data? How much CPU overhead will you tolerate?

 

 

The simplest "tune" to get you started is to use EXT4 with large block support. That tends to give you file writing speeds close to raw device.

 

To create such a filesystem (note: You'll need a Linux kernel > 3.2 to be able to run this command), pass the following options to mkfs.ext4: "-O bigalloc -C 262144"

This will give you 256k clusters (instead of the default 4k), which makes reading/writing large files have very little overhead (at the cost of each file taking up at least 256k...)

 

Mike.

0 Kudos
Highlighted
Newbie erubio
Newbie
1,527 Views
Registered: ‎02-27-2018

Re: SD card performance using Zynq SDIO and Linux, what data rates can be expected?

Hi Nick,

 

I do some test with different sd cards and I get data rates by reading of about 20 MBytes/s and by writing of 11 MBytes/s.  Somebody knows if I am doing something wrong by writing.... or it is the normal performance for the sd controller. Reading sounds goods to me but I would like to write faster.

0 Kudos