Re: [microblaze-uclinux] Performance microblaze vs. VirtexIIPro

[Matthew Rubenstein <email@xxxxxxxxxxxx>]

	Ensuring realtime synchrony is a top priority for embedded devices.
I/O, including TCP/IP, as well as the realtime clock itself, could be
"factored out" of the MB/uCL sequential kernel, and replaced with TCP/IP
& RTC device gate arrays operating in parallel with the rest of the
MB/uCL system. The kernel would call software hooks into those devices
instead of sequentially executing the original kernel instructions. That
would be a major win for the MB/uCL architecture over ASIC/uC
architectures, and point the way for other factored parallelism.


On Wed, 2004-05-12 at 02:19, John Williams wrote:
> Hi Josef, emanuel,
> 
> jozsef imrek wrote:
> 
> > On Tue, 11 May 2004, emanuel stiebler wrote:
> > 
> >>Anaybody out here made some tests what the performance in
> >>dhrystones is of this "chips" ?
> 
> > there is a config option in the uClinux-dist that you can use to have a
> > dhrystones test. i switchd it on, run the test (the header says: Dhrystone
> > Benchmark, Version 2.1 (Language: C) ).
> > 
> > the fpga is a xc2v1000fg456-4 runing at 66Mhz.
> > 
> > at boot time the kernel measures 3.19 BogoMIPS.
> 
> You can multiply this bogoMIPs by a factor of 10 if you enable the 
> instruction cache.  dcache has a very small effect, maybe <1 bogoMIPs.
> 
> > the result is 5035.0 dhrystones/sec (see attached output from the test).
> 
> Similarly the dhrystone measures are greatly improved if you enable the 
> icache - without it, and running from external DDR, poor little 
> microblaze lives in a perpetual pipeline stall.
> 
> A note on the dhrystones, and an item for the wishlist - there is a 
> problem with time accounting in the kernel - if you run dhrystone under 
> zero load, the system clock time reported for execution of the benchmark 
> is pretty accurate (compared to wall clock time).
> 
> If you place the kernel under a ping flood attack the reported system 
> time is unchanged, but the actual wall clock time doubles!
> 
> I've never looked further into it, but it certainly should be 
> straightened out, especially if you are relying on the system timer to 
> even vaguely represent true time.  This may be a common problem, which 
> could explain why people put RTC chips in their systems if it really 
> matters.  Comments?
> 
> Regards,
> 
> John
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-- 


(C) Matthew Rubenstein

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