James Foris wrote: > I have run into an issue with memory bandwidth using the Fedora Core > 2 kernels and I need help. I don't know what is wrong, but something > killed performance of my custom driver when I ported it from RedHat 7.3 > to Fedora Core 2. I believe I have narrowed it down to the kernel. > > My driver requires a large amount of contiguous physical memory for > DMA from a PCI device. I use the 'mem=YYY' command line parameter to > reserve the top of physical RAM for my driver. Then I allow mapping > via mmap() calls to user space. The user space app then uses this > pointer to save the data to disk. <snip> > I have tried this on several platforms and kernels and the results vary, > but the common denominator seems to be: > > Fedora kernel + 32-bit Intel = poor performance (see below) So this *isn't* a problem with Linus' 2.6 kernels from kernel.org? Wild guess: have you tried turning off the 4G+4G support in the kernel (requires a recompile)? HTH, James. -- E-mail address: james@ | Beam me up, Scotty, there's no intelligent life westexe.demon.co.uk | down here!
