On 10/04/2012 06:01 AM, Konrad Rzeszutek Wilk wrote: > On Wed, Oct 03, 2012 at 05:38:47PM -0700, Alexander Duyck wrote: >> In the case of swiotlb we already have the start of the region and the number >> of slabs that give us the region size. Instead of having to call >> virt_to_phys on two pointers we can just take advantage of the fact that the >> region is linear and just compute the end based on the start plus the size. > Why not take advantage of 'the fact that the region is linear' and just > pre-compute the end in swiotlb_init_with_tbl? > > That way the logic in is_swiotlb_buffer is even simpler? > Using a pre-computed end point based on a virtual address is more expensive in the x86_64 case. The calls to __phys_addr require a separate function call. By just using the physical address of the start and adding the offset I can avoid the second call and the compiler will take advantage of the smaller function size. The result is that is_swiotlb_buffer will be inlined. Thanks, Alex _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
