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Slow performance on samsung S3C6410

Marcin Jędrzejewski
Note: This was originally posted on 18th January 2011 at http://forums.arm.com

Hi,

I'am a software developer and I am trying to port our product to new device. This is Windows CE 6 device with S3C6410 (ARM1176JZF-S) CPU.  The problem is that Q-Bench benchmarks show that this is very fast system but after executing our application it is actually very slow.

I have spend a lot of time profiling various parts of our product, but it shows nothing. Finally what I have found out is that the problem is with the huge code amount. Actually our .exe is ~10MB in size. I have made tests in which I have auto generated huge amounts of code (~200,000 lines of c++ code, VS2005 compiled), and now executing this exe (~1.5MB) on this device shows significant slow down, 8 - 10 times comparing it to other devices (with slower CPUs). This auto generated code does nothing with data, it just executes lots of functions which just increment some variables.

My question is what is the source of problem? From What I know this CPU has  16 KiB instruction cache. Can it be somehow badly configured? I actually have no contact with this device manufacturer. I can only give some hints to its reseler to maybe push information further.

some more info:
Q-Bench Pro - shows that Cache Line == 8, while on other devices it is 32
CeGetCacheInfo - gives below results:
dwL1Flags=0
dwL1ICacheSize=16384
dwL1ICacheLineSize=32
dwL1ICacheNumWays=4
dwL1DCacheSize=16384
dwL1DCacheLineSize=32
dwL1DCacheNumWays=4
dwL2Flags=0
dwL2ICacheSize=0
dwL2ICacheLineSize=0
dwL2ICacheNumWays=0
dwL2DCacheSize=0
dwL2DCacheLineSize=0
dwL2DCacheNumWays=0

Thank You for any help
Martin
Parents
  • Note: This was originally posted on 25th January 2011 at http://forums.arm.com

    Thank You for your time, I dont really have any benchmarks of our application that would be of use here. Maybe the time of frame rendering, it gets nerly 2s on this device, while on others its 120ms-450ms. But it does a lot of memory reading and loading data from SD card. I have actually tested putting data from SD card to main memory (limited resource) on Windows CE but nothing changed.

    I started investigating this problem a little bit deeper and wrote a driver to read/write coprocessor registers. So far I have not found anything different from other platforms. With a bit of spare time I plan to use instruction cache miss event as described in "ARM11 performance monitor unit" article in knowledge base. It gives hint that high cache misses might be caused by disabled branch prediction.

    I suspect as You said that slow memory + small cache + fast CPU is the cause of the problem here. I know that our application works properly on Samsung Omnia 2 which uses this CPU, but it most probably uses other memory / sd card hardware configuration.

    Martin
Reply
  • Note: This was originally posted on 25th January 2011 at http://forums.arm.com

    Thank You for your time, I dont really have any benchmarks of our application that would be of use here. Maybe the time of frame rendering, it gets nerly 2s on this device, while on others its 120ms-450ms. But it does a lot of memory reading and loading data from SD card. I have actually tested putting data from SD card to main memory (limited resource) on Windows CE but nothing changed.

    I started investigating this problem a little bit deeper and wrote a driver to read/write coprocessor registers. So far I have not found anything different from other platforms. With a bit of spare time I plan to use instruction cache miss event as described in "ARM11 performance monitor unit" article in knowledge base. It gives hint that high cache misses might be caused by disabled branch prediction.

    I suspect as You said that slow memory + small cache + fast CPU is the cause of the problem here. I know that our application works properly on Samsung Omnia 2 which uses this CPU, but it most probably uses other memory / sd card hardware configuration.

    Martin
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