RAM disk size > 128MB on PandaBoard ES

Due to a recent fix to RamFS it’s now possible to get a working ram disk > 128MB on a Pandaboard ES. Previously it would just hang on boot.

Building an OMAP4 rom takes about 3minutes 50 seconds compared to about 7minutes using a USB SSD. A ram disk size of at least 384MB is needed.

Plus it take less than 30seconds to copy the build folder to the ram disk using !SyncDiscs.

Crikey. Sounds like we should do this on our autobuilder (cloud server running a clobbered version of RPCemu). Currently, that takes an hour to build the OMAP4 ROM image from clean…

Hmm, for that to work I guess we’d need some kind of Kinetic emulation in RPCEmu so that the machine can have >256MB of RAM.

Ah, I was hoping we could just frig it to have more RAM (and the IOMD image’s memory map) seeing as the actual RiscPC RAM size limits don’t really make sense in a VM.

Might be less effort (and expense in the long run) to replace the autobuild server with an OMAP4 board… :)

Well, updating RPCEmu might not be that difficult. It looks like they already cope with differing physical address space maps for IOMD vs. IOMD2, so it shouldn’t be too hard to add an extra config for the Kinetic.

Might be less effort (and expense in the long run) to replace the autobuild server with an OMAP4 board… :)

That would certainly be nice.

I have a feeling you’ll know the answer to this one, Chris: What’s the USB networking performance like at the moment? I.e. how long does it take to checkout a full build tree from within RISC OS, or to pull a build tree over an NFS share.

Due to a recent fix to RamFS it’s now possible to get a working ram disk > 128MB

I’d not have chosen the word ‘fix’, perhaps ‘shorttermist sticking plaster’. We really must wean ourselves off such wasteful uses of logical address space – to fritter 1/8th of the entire address space onto a RAM disc is pretty poor design. I think on the Iyonix that would mean you’ve run out of address space already if 1GB of RAM is fitted (less the PCI IO + PCI memory regions, dynamic areas, RMA & app slot), subject to my mental arithmetic.

I’m on the fence whether putting the RAM disc into the application slot or looking through a small window onto a large physical area is best, the latter sounds like it would decouple RAMFS from the application slot size limit, so perhaps that has the edge?

Fortunately, it’s been left at 128MB, and as it’s a variable it’s nice and easy to reduce it back to a sensible 16MB too.

I have a feeling you’ll know the answer to this one, Chris: What’s the USB networking performance like at the moment? I.e. how long does it take to checkout a full build tree from within RISC OS, or to pull a build tree over an NFS share.

Syncing over NFS from a Linux box using !SyncDiscs takes about four minutes.