nanogui: Speed Issues on a slow CPU
Subject:
Re: [nanogui] Speed Issues on a slow CPU
From:
Alan Cox ####@####.####
Date:
3 Oct 2007 13:52:38 +0100
Message-Id: <20071003135636.16003f36@the-village.bc.nu>
> I costed me several month and a lot of gcc hacking to reclaim this
> memory as general-purpose memory. So now we have a 36MByte uClinux
> system, with 32 MByte of this memory is a bit slower than usual.
I couldn't find info on this to see what its performance hit was or if
you have put a small graphics accelerator library on the ARM7
> I have nano-X and PIXIL up and running, but I am facing serious speed
> issues. The reaction to a click on the touchscreen is slow, and the
> calculator needs 1-2 seconds to display.
Thats slower than on an original IBM XT so bad
> What I have done so far:
> - define NDEBUG in nano-X drivers.
> - add assembler code for horizontal and vertical lines in the driver.
> - implement shared memory support.
Do you have gprof running on the system yet - embedded can have such
strange bottlenecks that gprof can reveal a lot - and you only need the
profiling side on the DS. You can do the analysis with cross tools on a
PC.
There are a couple of oddities I noted on the web site too btw:
"No. Because the NDS has no MMU, DSLinux has no virtual memory, so it
cannot swap at all."
Thats not totally true - you can swap entire apps to/from secondary
storage if you have any kind of segmentation (eg FCSE on
some ARM although the granularity is a bit high..) and/or PI code. You've
also presumably got protection ranges ?
BTW on
"Why doesn't DSLinux support reading from or writing to a CF"
if you've got specs for the CF interface and a tester thats probably easy
to fix now.
