Re: [PATCH v4 10/12] mm/gup: /proc/vmstat: pin_user_pages (FOLL_PIN) reporting
From: Jan Kara <jack@suse.cz>
Date: 2020-02-05 09:37:46
Also in:
linux-fsdevel, linux-kselftest, linux-mm, linux-rdma, lkml
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_released
These 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>...
quoted hunk ↗ jump to hunk
@@ -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 -- Jan Kara [off-list ref] SUSE Labs, CR