• John Hubbard's avatar
    mm/gup: /proc/vmstat: pin_user_pages (FOLL_PIN) reporting · 1970dc6f
    John Hubbard authored
    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: update Documentation/core-api/pin_user_pages.rst to rename the new
    /proc/vmstat entries, to the names listed here.
    Signed-off-by: default avatarJohn Hubbard <jhubbard@nvidia.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Reviewed-by: default avatarJan Kara <jack@suse.cz>
    Acked-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
    Cc: Ira Weiny <ira.weiny@intel.com>
    Cc: Jérôme Glisse <jglisse@redhat.com>
    Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Cc: Christoph Hellwig <hch@infradead.org>
    Cc: Dan Williams <dan.j.williams@intel.com>
    Cc: Dave Chinner <david@fromorbit.com>
    Cc: Jason Gunthorpe <jgg@ziepe.ca>
    Cc: Jonathan Corbet <corbet@lwn.net>
    Cc: Michal Hocko <mhocko@suse.com>
    Cc: Mike Kravetz <mike.kravetz@oracle.com>
    Cc: Shuah Khan <shuah@kernel.org>
    Cc: Vlastimil Babka <vbabka@suse.cz>
    Link: http://lkml.kernel.org/r/20200211001536.1027652-9-jhubbard@nvidia.comSigned-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    1970dc6f
mmzone.h 43.8 KB