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    Subject[PATCH v15 02/13] vmstat: add vmstat_idle function
    Date
    This function checks to see if a vmstat worker is not running,
    and the vmstat diffs don't require an update. The function is
    called from the task-isolation code to see if we need to
    actually do some work to quiet vmstat.

    Acked-by: Christoph Lameter <cl@linux.com>
    Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com>
    ---
    include/linux/vmstat.h | 2 ++
    mm/vmstat.c | 10 ++++++++++
    2 files changed, 12 insertions(+)

    diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
    index fab62aa74079..69b6cc4be909 100644
    --- a/include/linux/vmstat.h
    +++ b/include/linux/vmstat.h
    @@ -235,6 +235,7 @@ extern void __dec_node_state(struct pglist_data *, enum node_stat_item);

    void quiet_vmstat(void);
    void quiet_vmstat_sync(void);
    +bool vmstat_idle(void);
    void cpu_vm_stats_fold(int cpu);
    void refresh_zone_stat_thresholds(void);

    @@ -338,6 +339,7 @@ static inline void refresh_zone_stat_thresholds(void) { }
    static inline void cpu_vm_stats_fold(int cpu) { }
    static inline void quiet_vmstat(void) { }
    static inline void quiet_vmstat_sync(void) { }
    +static inline bool vmstat_idle(void) { return true; }

    static inline void drain_zonestat(struct zone *zone,
    struct per_cpu_pageset *pset) { }
    diff --git a/mm/vmstat.c b/mm/vmstat.c
    index 57fc29750da6..7dd17c06d3a7 100644
    --- a/mm/vmstat.c
    +++ b/mm/vmstat.c
    @@ -1763,6 +1763,16 @@ void quiet_vmstat_sync(void)
    }

    /*
    + * Report on whether vmstat processing is quiesced on the core currently:
    + * no vmstat worker running and no vmstat updates to perform.
    + */
    +bool vmstat_idle(void)
    +{
    + return !delayed_work_pending(this_cpu_ptr(&vmstat_work)) &&
    + !need_update(smp_processor_id());
    +}
    +
    +/*
    * Shepherd worker thread that checks the
    * differentials of processors that have their worker
    * threads for vm statistics updates disabled because of
    --
    2.7.2
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