lkml.org 
[lkml]   [2011]   [Dec]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    SubjectRe: Kswapd in 3.2.0-rc5 is a CPU hog
    From
    On Sat, Dec 24, 2011 at 4:45 AM, Dave Chinner <david@fromorbit.com> wrote:
    [...]
    >
    > Ok, it's not a shrink_slab() problem - it's just being called ~100uS
    > by kswapd. The pattern is:
    >
    >        - reclaim 94 (batches of 32,32,30) pages from iinactive list
    >          of zone 1, node 0, prio 12
    >        - call shrink_slab
    >                - scan all caches
    >                - all shrinkers return 0 saying nothing to shrink
    >        - 40us gap
    >        - reclaim 10-30 pages from inactive list of zone 2, node 0, prio 12
    >        - call shrink_slab
    >                - scan all caches
    >                - all shrinkers return 0 saying nothing to shrink
    >        - 40us gap
    >        - isolate 9 pages from LRU zone ?, node ?, none isolated, none freed
    >        - isolate 22 pages from LRU zone ?, node ?, none isolated, none freed
    >        - call shrink_slab
    >                - scan all caches
    >                - all shrinkers return 0 saying nothing to shrink
    >        40us gap
    >
    > And it just repeats over and over again. After a while, nid=0,zone=1
    > drops out of the traces, so reclaim only comes in batches of 10-30
    > pages from zone 2 between each shrink_slab() call.
    >
    > The trace starts at 111209.881s, with 944776 pages on the LRUs. It
    > finishes at 111216.1 with kswapd going to sleep on node 0 with
    > 930067 pages on the LRU. So 7 seconds to free 15,000 pages (call it
    > 2,000 pages/s) which is awfully slow....
    >
    Hi all,

    In hope, the added debug info is helpful.

    Hillf
    ---

    --- a/mm/memcontrol.c Fri Dec 9 21:57:40 2011
    +++ b/mm/memcontrol.c Sun Dec 25 17:08:14 2011
    @@ -1038,7 +1038,11 @@ void mem_cgroup_lru_del_list(struct page
    memcg = root_mem_cgroup;
    mz = page_cgroup_zoneinfo(memcg, page);
    /* huge page split is done under lru_lock. so, we have no races. */
    - MEM_CGROUP_ZSTAT(mz, lru) -= 1 << compound_order(page);
    + if (WARN_ON_ONCE(MEM_CGROUP_ZSTAT(mz, lru) <
    + (1 << compound_order(page))))
    + MEM_CGROUP_ZSTAT(mz, lru) = 0;
    + else
    + MEM_CGROUP_ZSTAT(mz, lru) -= 1 << compound_order(page);
    }

    void mem_cgroup_lru_del(struct page *page)
    --
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/
    \
     
     \ /
      Last update: 2011-12-25 10:13    [W:0.036 / U:30.568 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site