Re: [PATCH 0/3] resource: find_next_iomem_res() improvements

From: Dan Williams
Date: Tue Jun 18 2019 - 02:49:45 EST

On Wed, Jun 12, 2019 at 9:59 PM Nadav Amit <namit@xxxxxxxxxx> wrote:
> Running some microbenchmarks on dax keeps showing find_next_iomem_res()
> as a place in which significant amount of time is spent. It appears that
> in order to determine the cacheability that is required for the PTE,
> lookup_memtype() is called, and this one traverses the resources list in
> an inefficient manner. This patch-set tries to improve this situation.

Let's just do this lookup once per device, cache that, and replay it
to modified vmf_insert_* routines that trust the caller to already
know the pgprot_values.