• Hugh Dickins's avatar
    mm: take pagevecs off reclaim stack · 2bcf8879
    Hugh Dickins authored
    Replace pagevecs in putback_lru_pages() and move_active_pages_to_lru()
    by lists of pages_to_free: then apply Konstantin Khlebnikov's
    free_hot_cold_page_list() to them instead of pagevec_release().
    
    Which simplifies the flow (no need to drop and retake lock whenever
    pagevec fills up) and reduces stale addresses in stack backtraces
    (which often showed through the pagevecs); but more importantly,
    removes another 120 bytes from the deepest stacks in page reclaim.
    Although I've not recently seen an actual stack overflow here with
    a vanilla kernel, move_active_pages_to_lru() has often featured in
    deep backtraces.
    
    However, free_hot_cold_page_list() does not handle compound pages
    (nor need it: a Transparent HugePage would have been split by the
    time it reaches the call in shrink_page_list()), but it is possible
    for putback_lru_pages() or move_active_pages_to_lru() to be left
    holding the last reference on a THP, so must exclude the unlikely
    compound case before putting on pages_to_free.
    
    Remove pagevec_strip(), its work now done in move_active_pages_to_lru().
    The pagevec in scan_mapping_unevictable_pages() remains in mm/vmscan.c,
    but that is never on the reclaim path, and cannot be replaced by a list.
    Signed-off-by: default avatarHugh Dickins <hughd@google.com>
    Reviewed-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    Reviewed-by: default avatarKonstantin Khlebnikov <khlebnikov@openvz.org>
    Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Cc: Mel Gorman <mel@csn.ul.ie>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    2bcf8879
vmscan.c 103 KB