On 07/26/2018 03:42 PM, Matthew Wilcox wrote: > 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. > Thanks for the tip. I will give that a try.
