On Tue, Oct 10, 2006 at 10:19:04AM +0100, Christoph Hellwig wrote: > On Mon, Oct 09, 2006 at 09:15:28PM -0500, Steve Lord wrote: > > Hi Dave, > > > > My recollection is that it used to default to on, it was disabled > > because it needs to map the buffer into a single contiguous chunk > > of kernel memory. This was placing a lot of pressure on the memory > > remapping code, so we made it not default to on as reworking the > > code to deal with non contig memory was looking like a major > > effort. > > Exactly. The code works but tends to go OOM pretty fast at least > when the dir blocksize code is bigger than the page size. I should > give the code a spin on my ppc box with 64k pages if it works better > there. The pagebuf code doesn't use high-order allocations anymore; it uses scatter lists and remapping to allow physically discontiguous pages in a multi-page buffer. That is, the pages are sourced via find_or_create_page() from the address space of the backing device, and then mapped via vmap() to provide a virtually contigous mapping of the multi-page buffer. So I don't think this problem exists anymore... Cheers, Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
