On 3/7/07, Ralf Baechle <[EMAIL PROTECTED]> wrote:
GFP_* flags have no influence on caching or prefetching.
The zone modifier flags (like GFP_DMA) can in principle affect the cache/prefetch policy, since they affect what physical address range the memory is allocated from. I don't know whether Linux uses this effect intentionally, but I would not be the least bit surprised if virtual machines commonly treat the traditional 16MB of low physical memory differently from the rest of the address space. Looking at the i386 implementation of dma_alloc_coherent (underlying pci_alloc_consistent), it's not clear to me how this interferes with cacheability of the allocated block. Maybe it doesn't. The alpha version of pci_alloc_consistent, on the other hand, does interesting things to make the memory visible to PCI. Don, what arches did you have in mind when you commented on caching issues? Cheers, - Michael - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
