Re: [PATCH v4 3/5] dax: use common 4k zero page for dax mmap reads

2017-07-24 Thread Jan Kara
On Fri 21-07-17 16:39:53, Ross Zwisler wrote: > When servicing mmap() reads from file holes the current DAX code allocates > a page cache page of all zeroes and places the struct page pointer in the > mapping->page_tree radix tree. This has three major drawbacks: > > 1) It consumes memory unneces

[PATCH v4 3/5] dax: use common 4k zero page for dax mmap reads

2017-07-21 Thread Ross Zwisler
When servicing mmap() reads from file holes the current DAX code allocates a page cache page of all zeroes and places the struct page pointer in the mapping->page_tree radix tree. This has three major drawbacks: 1) It consumes memory unnecessarily. For every 4k page that is read via a DAX mmap()