• Kirill Tkhai's avatar
    mm, memcg: assign memcg-aware shrinkers bitmap to memcg · 0a4465d3
    Kirill Tkhai authored
    Imagine a big node with many cpus, memory cgroups and containers.  Let
    we have 200 containers, every container has 10 mounts, and 10 cgroups.
    All container tasks don't touch foreign containers mounts.  If there is
    intensive pages write, and global reclaim happens, a writing task has to
    iterate over all memcgs to shrink slab, before it's able to go to
    shrink_page_list().
    
    Iteration over all the memcg slabs is very expensive: the task has to
    visit 200 * 10 = 2000 shrinkers for every memcg, and since there are
    2000 memcgs, the total calls are 2000 * 2000 = 4000000.
    
    So, the shrinker makes 4 million do_shrink_slab() calls just to try to
    isolate SWAP_CLUSTER_MAX pages in one of the actively writing memcg via
    shrink_page_list().  I've observed a node spending almost 100% in
    kernel, making useless iteration over already shrinked slab.
    
    This patch adds bitmap of memcg-aware shrinkers to memcg.  The size of
    the bitmap depends on bitmap_nr_ids, and during memcg life it's
    maintained to be enough to fit bitmap_nr_ids shrinkers.  Every bit in
    the map is related to corresponding shrinker id.
    
    Next patches will maintain set bit only for really charged memcg.  This
    will allow shrink_slab() to increase its performance in significant way.
    See the last patch for the numbers.
    
    [ktkhai@virtuozzo.com: v9]
      Link: http://lkml.kernel.org/r/153112549031.4097.3576147070498769979.stgit@localhost.localdomain
    [ktkhai@virtuozzo.com: add comment to mem_cgroup_css_online()]
      Link: http://lkml.kernel.org/r/521f9e5f-c436-b388-fe83-4dc870bfb489@virtuozzo.com
    Link: http://lkml.kernel.org/r/153063056619.1818.12550500883688681076.stgit@localhost.localdomainSigned-off-by: default avatarKirill Tkhai <ktkhai@virtuozzo.com>
    Acked-by: default avatarVladimir Davydov <vdavydov.dev@gmail.com>
    Tested-by: default avatarShakeel Butt <shakeelb@google.com>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
    Cc: Chris Wilson <chris@chris-wilson.co.uk>
    Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Cc: Guenter Roeck <linux@roeck-us.net>
    Cc: "Huang, Ying" <ying.huang@intel.com>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: Josef Bacik <jbacik@fb.com>
    Cc: Li RongQing <lirongqing@baidu.com>
    Cc: Matthew Wilcox <willy@infradead.org>
    Cc: Matthias Kaehlcke <mka@chromium.org>
    Cc: Mel Gorman <mgorman@techsingularity.net>
    Cc: Michal Hocko <mhocko@kernel.org>
    Cc: Minchan Kim <minchan@kernel.org>
    Cc: Philippe Ombredanne <pombredanne@nexb.com>
    Cc: Roman Gushchin <guro@fb.com>
    Cc: Sahitya Tummala <stummala@codeaurora.org>
    Cc: Stephen Rothwell <sfr@canb.auug.org.au>
    Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Waiman Long <longman@redhat.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    0a4465d3
memcontrol.c 168 KB