On 7/20/05, Erik Mouw <[EMAIL PROTECTED]> wrote: > On Wed, Jul 20, 2005 at 01:35:07PM +0000, Miquel van Smoorenburg wrote: > > In article <[EMAIL PROTECTED]>, > > Erik Mouw <[EMAIL PROTECTED]> wrote: > > >On Wed, Jul 20, 2005 at 02:16:36PM +0200, Bastiaan Naber wrote: > > >AFAIK you can't use a 15 GB tmpfs on i386 because large memory support > > >is basically a hack to support multiple 4GB memory spaces (some VM guru > > >correct me if I'm wrong). > > > > I'm no VM guru but I have a 32 bit machine here with 8 GB of > > memory and 8 GB of swap: > > > > # mount -t tmpfs -o size=$((12*1024*1024*1024)) tmpfs /mnt > > # df > > Filesystem 1K-blocks Used Available Use% Mounted on > > /dev/sda1 19228276 1200132 17051396 7% / > > tmpfs 12582912 0 12582912 0% /mnt > > > > There you go, a 12 GB tmpfs. I haven't tried to create a 12 GB > > file on it, though, since this is a production machine and it > > needs the memory .. > > I stand corrected. > > > So yes that appears to work just fine. > > The question is if it's a good idea to use a 15GB tmpfs on a 32 bit > i386 class machine. I guess a real 64 bit machine will be much faster > in handling suchs amounts of data simply because you don't have to go > through the hurdles needed to address such memory on i386. > > > Erik >
On 32bit: you would have to use read() and write() or mmap() munmap() mremap() to perform your own paging, since you can't fit 15GB on a 4GB address space. On 64bit: you would simply mmap() the whole file and you are done. Most probably the cost of programming and debugging the hand-made paging on 32bit machines will cost more than the difference for a 64bit machine. -- Greetz, Antonio Vargas aka winden of network http://wind.codepixel.com/ Las cosas no son lo que parecen, excepto cuando parecen lo que si son. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
