Re: [PATCH 0/3] remove rw_page() from brd, pmem and btt

[Christoph Hellwig]

On Mon, Jul 31, 2017 at 07:16:59AM +0900, Minchan Kim wrote:
> rw_page's gain is reducing of dynamic allocation in swap path
> as well as performance gain thorugh avoiding bio allocation.
> And it would be important in memory pressure situation.

There is no need for any dynamic allocation when using the bio
path.  Take a look at __blkdev_direct_IO_simple for an example
that doesn't do any allocations.