On Tue 04-02-20 15:41:15, 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
...
@@ -104,6 +106,9 @@ static __maybe_unused struct page *try_grab_compound_head(struct page *page, if (hpage_pincount_available(page)) hpage_pincount_add(page, refs);
mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_ACQUIRED,orig_refs);- return page; }
It seems to me you miss mod_node_page_state() in put_compound_head(), don't you?
Otherwise I like the new stat names better :).
Honza