• KAMEZAWA Hiroyuki's avatar
    memcg: fix get_scan_count() for small targets · 246e87a9
    KAMEZAWA Hiroyuki authored
    During memory reclaim we determine the number of pages to be scanned per
    zone as
    
    	(anon + file) >> priority.
    Assume
    	scan = (anon + file) >> priority.
    
    If scan < SWAP_CLUSTER_MAX, the scan will be skipped for this time and
    priority gets higher.  This has some problems.
    
      1. This increases priority as 1 without any scan.
         To do scan in this priority, amount of pages should be larger than 512M.
         If pages>>priority < SWAP_CLUSTER_MAX, it's recorded and scan will be
         batched, later. (But we lose 1 priority.)
         If memory size is below 16M, pages >> priority is 0 and no scan in
         DEF_PRIORITY forever.
    
      2. If zone->all_unreclaimabe==true, it's scanned only when priority==0.
         So, x86's ZONE_DMA will never be recoverred until the user of pages
         frees memory by itself.
    
      3. With memcg, the limit of memory can be small. When using small memcg,
         it gets priority < DEF_PRIORITY-2 very easily and need to call
         wait_iff_congested().
         For doing scan before priorty=9, 64MB of memory should be used.
    
    Then, this patch tries to scan SWAP_CLUSTER_MAX of pages in force...when
    
      1. the target is enough small.
      2. it's kswapd or memcg reclaim.
    
    Then we can avoid rapid priority drop and may be able to recover
    all_unreclaimable in a small zones.  And this patch removes nr_saved_scan.
     This will allow scanning in this priority even when pages >> priority is
    very small.
    Signed-off-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Acked-by: default avatarYing Han <yinghan@google.com>
    Cc: Balbir Singh <balbir@in.ibm.com>
    Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
    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>
    246e87a9
page_alloc.c 158 KB