On 01/09/06, Ricard Wanderlof <ricard.wanderlof@xxxxxxxx> wrote:
Hi, I came across a problem in the mtd nand flash driver for Linux 2.6.16, where the driver tries to allocate about 135k using kmalloc. Now, it used to be that kmalloc couldn't handle more than 128k, but for instance looking in the 3rd edition of Linux Device Drivers, it more cryptically says that 128k is guaranteed, but the depending on the architecture and kernel version. I have not yet dived into the code, but does anyone know what this limitation was historically, why it has changed and what governs it in the later kernels?
kmalloc() allocates physically contiguous pages, so fragmentation of memory over time limits how large chunks you can get. If you don't require the memory to be physically contiguous but merely that it be logically contiguous, then you can use vmalloc() which allocates memory that is not guarenteed to be physically contiguous (so you can't use it for DMA for instance, and it's a bit slower), but it'll be logically contiguous. vmalloc() can get you larger chunks than kmalloc(). -- Jesper Juhl <jesper.juhl@xxxxxxxxx> Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html Plain text mails only, please http://www.expita.com/nomime.html -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
