On Thu, Feb 06, 2020 at 07:37:33PM -0800, John Hubbard wrote:
Now that pages are "DMA-pinned" via pin_user_page*(), and unpinned via unpin_user_pages*(), we need some visibility into whether all of this is working correctly.
Add two new fields to /proc/vmstat:
nr_foll_pin_acquired nr_foll_pin_releasedThese are documented in Documentation/core-api/pin_user_pages.rst. They represent the number of pages (since boot time) that have been pinned ("nr_foll_pin_acquired") and unpinned ("nr_foll_pin_released"), via pin_user_pages*() and unpin_user_pages*().
In the absence of long-running DMA or RDMA operations that hold pages pinned, the above two fields will normally be equal to each other.
Also: update Documentation/core-api/pin_user_pages.rst, to remove an earlier (now confirmed untrue) claim about a performance problem with /proc/vmstat.
Also: updated Documentation/core-api/pin_user_pages.rst to rename the new /proc/vmstat entries, to the names listed here.
Signed-off-by: John Hubbard jhubbard@nvidia.com
Acked-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com