> On Jun 17, 2019, at 11:44 PM, Dan Williams <[email protected]> wrote: > > On Wed, Jun 12, 2019 at 9:59 PM Nadav Amit <[email protected]> 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.
IIUC, one device can have multiple regions with different characteristics, which require difference cachability. Apparently, that is the reason there is a tree of resources. Please be more specific about where you want to cache it, please. Perhaps you want to cache the cachability-mode in vma->vm_page_prot (which I see being done in quite a few cases), but I don’t know the code well enough to be certain that every vma should have a single protection and that it should not change afterwards.
