On Sunday 01 October 2006 22:40, James Bottomley wrote: > On Sun, 2006-10-01 at 22:13 +0200, Andi Kleen wrote: > > GFP_DMA in general is deprecated and should be replaced by appropiate > > dma_alloc_coherent() > > Um, no it shouldn't > > All of the places where we use GFP_DMA are because we might be > addressing an ISA card or other strange mask limited card (gated usually > by unchecked_isa_dma). This means the majority of drivers will never use it? I don't claim to be a SCSI expert, but a lot of uses looked unchecked to me from a quick look. That is very worrying because it's only 16MB on x86 and 16MB run out quickly. If it's never used I don't care that much, but it certainly doesn't look like that. Or do you only need it because pci_map_single() on i386 doesn't do bouncing? If yes we can probably fix that. > However, what is wanted in every case is > ordinary memory, not coherent memory. They can't simply be replaced > with dma_alloc_coherent because > > a) it will waste memory for platforms that only do it in page size > multiples > b) It will fail on platforms that can't do it at all. GFP_DMA will also fail on a lot of platforms, so it's the same. > Coherent memory is really only for device drivers to use in mailboxes > and shared ring buffers. Maybe we need a new interface then with a mask. The plan is anyways get rid of GFP_DMA completely because it has lots of problems. And any user should declare the mask it really needs. -Andi - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
