On Thu, Oct 1, 2009 at 7:56 PM, Bart Veer <[email protected]> wrote: >>>>>> "Mandeep" == Mandeep Sandhu <[email protected]> writes: > > Mandeep> Look at the size output for the _same_ app compiled with > Mandeep> the Linux Synthetic target: > > Mandeep> $ i386-elf-size myapp > Mandeep> text data bss dec hex filename > Mandeep> 103690 7328 8381268 8492286 8194fe myapp > > Mandeep> The text size of the ARM binary (~127KB) is > Mandeep> understandably larger than the i386 one (~102 KB). > > Mandeep> But how come the data+bss value is so different!?!? The > Mandeep> i386 one is more than 8MB! > > Mandeep> Is this expected? I'm still googling to find the answer. > > On real embedded targets the memory is physical. Not so on the > synthetic target. Somehow or other the executable's ELF header info > must tell the Linux OS to allocate 8MB of memory for the emulated > target's RAM. Without that things like malloc() would not work, at > least not without playing nasty games with mmap() at run-time. The > easiest way to make things work is to make it seem like data+bss > occupy all of 8MB, irrespective of the application's actual static > data requirements. The surplus over 8MB reported by size is likely to > be const data and the like which the linker script places in the > read-only code region. > > This could probably be fixed if it was really necessary, but it would > be non-trivial and I don't recall anybody reporting the issue in the > past. Generally memory usage on the synthetic target will not give an > accurate indication of memory usage on real targets because of the > need for much larger stack sizes etc. - I won't go into all the > unpleasant details.
Thanks Bart. This explains it. It's not an issue for me, was just curious to know. Regards, -mandeep > > Bart > > -- > Bart Veer eCos Configuration Architect > eCosCentric Limited The eCos experts http://www.ecoscentric.com/ > Barnwell House, Barnwell Drive, Cambridge, UK. Tel: +44 1223 245571 > Registered in England and Wales: Reg No 4422071. > >>>> Visit us at ESC-UK http://www.embedded.co.uk <<<< > >>>> Oct 7-8 on Stand 433 at FIVE ISC, Farnborough <<<< > -- Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss
