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Slow performance on samsung S3C6410

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

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Marcin Jędrzejewski over 12 years ago

Note: This was originally posted on 1st December 2011 at http://forums.arm.com

From TCM status register I have read that there are two Data and two Instruction TCMs. They are 8KB in size. From TCM Region Register I have read that both Data TCMs are enabled, and both Instruction TCMs are disabled.

I will give it a try and try enabling ITCM but I am not quite sure how it will work. I am a Windows CE application developer, I am not able to modify system on device in any way. All I can do is to set Region Register for Instruction TCM with some base address (using self made device driver). From what I have read it is not a general purpose cache but it is supposed to be explicitly used by the system developer to speed up code for handling interrupts etc. Is it true? Or maybe enabling it will make CPU use some more cache for processing instructions from our application? I am not sure if it is our application that is being slowed down or windows ce is just slow on this device.

Martin

[Edit] - not 16KB but 8KB
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Marcin Jędrzejewski over 12 years ago

Note: This was originally posted on 1st December 2011 at http://forums.arm.com

From TCM status register I have read that there are two Data and two Instruction TCMs. They are 8KB in size. From TCM Region Register I have read that both Data TCMs are enabled, and both Instruction TCMs are disabled.

I will give it a try and try enabling ITCM but I am not quite sure how it will work. I am a Windows CE application developer, I am not able to modify system on device in any way. All I can do is to set Region Register for Instruction TCM with some base address (using self made device driver). From what I have read it is not a general purpose cache but it is supposed to be explicitly used by the system developer to speed up code for handling interrupts etc. Is it true? Or maybe enabling it will make CPU use some more cache for processing instructions from our application? I am not sure if it is our application that is being slowed down or windows ce is just slow on this device.

Martin

[Edit] - not 16KB but 8KB
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