2009-04-16 10:18:44     Performance differences

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2009-04-16 10:18:44     Performance differences

Harbhajan Singh (INDIA)

Message: 72758   




I have two hardware platforms with BF533 and BF527 with similar pheripherals Interfaced. I am working with the distribution 2008R1.5.


I have builded the uImage for the BF533 and BF527.


I run the same application after booting the kernel in BF527 and Bf533 platforms.


I observed the cpu usage using the top command. i obsered that there is a 15% difference for BF533 and BF527.


BF527 is usage 15% more compared with the BF533 platform. what could be the reason?


I have done the statistical profoling for both the platforms, I observed that the difference is 5-6% only  in the free mips availability. ( The % of time executed for IDLE instruction ).


our understanding is that execution of IDLE instruction gives free mips is correct or not?


How to relate the top and statistical profling results?


- Harbhajan




2009-04-17 14:46:59     Re: Performance differences


Message: 72795   




I don't think that anyone has ever looked to see how really accurate top is - so I'm not sure what could be going on.


Fundamentally - there shouldn't be much different between 533 and 527 which would impact performance.






2009-04-17 16:05:18     Re: Performance differences


Message: 72803   




After thinking about this a little more - it is likely that the PPI DMA from U-Boot's splash screen is active. (Or you have /dev/fb turned on in the kernel?)


If so - that is why - the DMA for the PPI is causing core memory read/writes to be delayed.






2009-04-18 04:55:19     Re: Performance differences

Harbhajan Singh (INDIA)

Message: 72817   


Hi Robin,




In BF533 and BF527 we use the PPI DMA core memory writes. and also the BF527 has the less data cache memory compared to the BF533 is this an issue?


Please let us know are there any we are overlooking.










2009-04-20 20:26:00     Re: Performance differences

Mike Frysinger (UNITED STATES)

Message: 72915   


the BF527 and BF533 have the exact same amounts of on-chip memory (cached and sram)


the cores should function the same, but the peripherals will have seen different fixes.  try disabling peripheral usage and compare the base lines first before adding in the entire system.