On Thu, Jul 26, 2018 at 02:54:56PM -0400, Tony Battersby wrote: > dma_pool_free() scales poorly when the pool contains many pages because > pool_find_page() does a linear scan of all allocated pages. Improve its > scalability by replacing the linear scan with a red-black tree lookup. > In big O notation, this improves the algorithm from O(n^2) to O(n * log n). This is a lot of code to get us to O(n * log(n)) when we can use less code to go to O(n). dma_pool_free() is passed the virtual address. We can go from virtual address to struct page with virt_to_page(). In struct page, we have 5 words available (20/40 bytes), and it's trivial to use one of them to point to the struct dma_page.
