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    vmstat: do not use deferrable delayed work for vmstat_update · ba4877b9
    Michal Hocko 提交于
    Vinayak Menon has reported that an excessive number of tasks was throttled
    in the direct reclaim inside too_many_isolated() because NR_ISOLATED_FILE
    was relatively high compared to NR_INACTIVE_FILE.  However it turned out
    that the real number of NR_ISOLATED_FILE was 0 and the per-cpu
    vm_stat_diff wasn't transferred into the global counter.
    
    vmstat_work which is responsible for the sync is defined as deferrable
    delayed work which means that the defined timeout doesn't wake up an idle
    CPU.  A CPU might stay in an idle state for a long time and general effort
    is to keep such a CPU in this state as long as possible which might lead
    to all sorts of troubles for vmstat consumers as can be seen with the
    excessive direct reclaim throttling.
    
    This patch basically reverts 39bf6270 ("VM statistics: Make timer
    deferrable") but it shouldn't cause any problems for idle CPUs because
    only CPUs with an active per-cpu drift are woken up since 7cc36bbd
    ("vmstat: on-demand vmstat workers v8") and CPUs which are idle for a
    longer time shouldn't have per-cpu drift.
    
    Fixes: 39bf6270 (VM statistics: Make timer deferrable)
    Signed-off-by: NMichal Hocko <mhocko@suse.cz>
    Reported-by: NVinayak Menon <vinmenon@codeaurora.org>
    Acked-by: NChristoph Lameter <cl@linux.com>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: Vladimir Davydov <vdavydov@parallels.com>
    Cc: Mel Gorman <mgorman@suse.de>
    Cc: Minchan Kim <minchan@kernel.org>
    Cc: David Rientjes <rientjes@google.com>
    Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
    ba4877b9
vmstat.c 40.7 KB