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    SubjectRe: [PATCH 1/2] Resource usage threshold notification addition to res_counter (v3)
    From
    As I mentioned in another thread, I think that associating the
    threshold with the res_counter rather than with each individual waiter
    is a mistake, since it creates global state and makes it hard to have
    multiple waiters on the same cgroup.

    Paul

    On Mon, Jul 13, 2009 at 5:16 PM, Vladislav
    Buzov<vbuzov@embeddedalley.com> wrote:
    > This patch updates the Resource Counter to add a configurable resource usage
    > threshold notification mechanism.
    >
    > Signed-off-by: Vladislav Buzov <vbuzov@embeddedalley.com>
    > Signed-off-by: Dan Malek <dan@embeddedalley.com>
    > ---
    >  Documentation/cgroups/resource_counter.txt |   21 ++++++++-
    >  include/linux/res_counter.h                |   69 ++++++++++++++++++++++++++++
    >  kernel/res_counter.c                       |    7 +++
    >  3 files changed, 95 insertions(+), 2 deletions(-)
    >
    > diff --git a/Documentation/cgroups/resource_counter.txt b/Documentation/cgroups/resource_counter.txt
    > index 95b24d7..1369dff 100644
    > --- a/Documentation/cgroups/resource_counter.txt
    > +++ b/Documentation/cgroups/resource_counter.txt
    > @@ -39,7 +39,20 @@ to work with it.
    >        The failcnt stands for "failures counter". This is the number of
    >        resource allocation attempts that failed.
    >
    > - c. spinlock_t lock
    > + e. unsigned long long threshold
    > +
    > +       The resource usage threshold to notify the resouce controller. This is
    > +       the minimal difference between the resource limit and current usage
    > +       to fire a notification.
    > +
    > + f. void (*threshold_notifier)(struct res_counter *counter)
    > +
    > +       The threshold notification callback installed by the resource
    > +       controller. Called when the usage reaches or exceeds the threshold.
    > +       Should be fast and not sleep because called when interrupts are
    > +       disabled.
    > +
    > + g. spinlock_t lock
    >
    >        Protects changes of the above values.
    >
    > @@ -140,6 +153,7 @@ counter fields. They are recommended to adhere to the following rules:
    >        usage           usage_in_<unit_of_measurement>
    >        max_usage       max_usage_in_<unit_of_measurement>
    >        limit           limit_in_<unit_of_measurement>
    > +       threshold       notify_threshold_in_<unit_of_measurement>
    >        failcnt         failcnt
    >        lock            no file :)
    >
    > @@ -153,9 +167,12 @@ counter fields. They are recommended to adhere to the following rules:
    >        usage           prohibited
    >        max_usage       reset to usage
    >        limit           set the limit
    > +       threshold       set the threshold
    >        failcnt         reset to zero
    >
    > -
    > + d. Notification is enabled by installing the threshold notifier callback. It
    > +    is up to the resouce controller to communicate the notification to user
    > +    space tasks.
    >
    >  5. Usage example
    >
    > diff --git a/include/linux/res_counter.h b/include/linux/res_counter.h
    > index 511f42f..5ec98d7 100644
    > --- a/include/linux/res_counter.h
    > +++ b/include/linux/res_counter.h
    > @@ -9,6 +9,11 @@
    >  *
    >  * Author: Pavel Emelianov <xemul@openvz.org>
    >  *
    > + * Resouce usage threshold notification update
    > + * Copyright 2009 CE Linux Forum and Embedded Alley Solutions, Inc.
    > + * Author: Dan Malek <dan@embeddedalley.com>
    > + * Author: Vladislav Buzov <vbuzov@embeddedalley.com>
    > + *
    >  * See Documentation/cgroups/resource_counter.txt for more
    >  * info about what this counter is.
    >  */
    > @@ -35,6 +40,19 @@ struct res_counter {
    >         */
    >        unsigned long long limit;
    >        /*
    > +        * the resource usage threshold to notify the resouce controller. This
    > +        * is the minimal difference between the resource limit and current
    > +        * usage to fire a notification.
    > +        */
    > +       unsigned long long threshold;
    > +       /*
    > +        * the threshold notification callback installed by the resource
    > +        * controller. Called when the usage reaches or exceeds the threshold.
    > +        * Should be fast and not sleep because called when interrupts are
    > +        * disabled.
    > +        */
    > +       void (*threshold_notifier)(struct res_counter *counter);
    > +       /*
    >         * the number of unsuccessful attempts to consume the resource
    >         */
    >        unsigned long long failcnt;
    > @@ -87,6 +105,7 @@ enum {
    >        RES_MAX_USAGE,
    >        RES_LIMIT,
    >        RES_FAILCNT,
    > +       RES_THRESHOLD,
    >  };
    >
    >  /*
    > @@ -132,6 +151,21 @@ static inline bool res_counter_limit_check_locked(struct res_counter *cnt)
    >        return false;
    >  }
    >
    > +static inline bool res_counter_threshold_check_locked(struct res_counter *cnt)
    > +{
    > +       if (cnt->usage + cnt->threshold < cnt->limit)
    > +               return true;
    > +
    > +       return false;
    > +}
    > +
    > +static inline void res_counter_threshold_notify_locked(struct res_counter *cnt)
    > +{
    > +       if (!res_counter_threshold_check_locked(cnt) &&
    > +           cnt->threshold_notifier)
    > +               cnt->threshold_notifier(cnt);
    > +}
    > +
    >  /*
    >  * Helper function to detect if the cgroup is within it's limit or
    >  * not. It's currently called from cgroup_rss_prepare()
    > @@ -147,6 +181,21 @@ static inline bool res_counter_check_under_limit(struct res_counter *cnt)
    >        return ret;
    >  }
    >
    > +/*
    > + * Helper function to detect if the cgroup usage is under it's threshold or
    > + * not.
    > + */
    > +static inline bool res_counter_check_under_threshold(struct res_counter *cnt)
    > +{
    > +       bool ret;
    > +       unsigned long flags;
    > +
    > +       spin_lock_irqsave(&cnt->lock, flags);
    > +       ret = res_counter_threshold_check_locked(cnt);
    > +       spin_unlock_irqrestore(&cnt->lock, flags);
    > +       return ret;
    > +}
    > +
    >  static inline void res_counter_reset_max(struct res_counter *cnt)
    >  {
    >        unsigned long flags;
    > @@ -174,6 +223,26 @@ static inline int res_counter_set_limit(struct res_counter *cnt,
    >        spin_lock_irqsave(&cnt->lock, flags);
    >        if (cnt->usage <= limit) {
    >                cnt->limit = limit;
    > +               if (limit <= cnt->threshold)
    > +                       cnt->threshold = 0;
    > +               else
    > +                       res_counter_threshold_notify_locked(cnt);
    > +               ret = 0;
    > +       }
    > +       spin_unlock_irqrestore(&cnt->lock, flags);
    > +       return ret;
    > +}
    > +
    > +static inline int res_counter_set_threshold(struct res_counter *cnt,
    > +               unsigned long long threshold)
    > +{
    > +       unsigned long flags;
    > +       int ret = -EINVAL;
    > +
    > +       spin_lock_irqsave(&cnt->lock, flags);
    > +       if (cnt->limit > threshold) {
    > +               cnt->threshold = threshold;
    > +               res_counter_threshold_notify_locked(cnt);
    >                ret = 0;
    >        }
    >        spin_unlock_irqrestore(&cnt->lock, flags);
    > diff --git a/kernel/res_counter.c b/kernel/res_counter.c
    > index e1338f0..9b36748 100644
    > --- a/kernel/res_counter.c
    > +++ b/kernel/res_counter.c
    > @@ -5,6 +5,10 @@
    >  *
    >  * Author: Pavel Emelianov <xemul@openvz.org>
    >  *
    > + * Resouce usage threshold notification update
    > + * Copyright 2009 CE Linux Forum and Embedded Alley Solutions, Inc.
    > + * Author: Dan Malek <dan@embeddedalley.com>
    > + * Author: Vladislav Buzov <vbuzov@embeddedalley.com>
    >  */
    >
    >  #include <linux/types.h>
    > @@ -32,6 +36,7 @@ int res_counter_charge_locked(struct res_counter *counter, unsigned long val)
    >        counter->usage += val;
    >        if (counter->usage > counter->max_usage)
    >                counter->max_usage = counter->usage;
    > +       res_counter_threshold_notify_locked(counter);
    >        return 0;
    >  }
    >
    > @@ -101,6 +106,8 @@ res_counter_member(struct res_counter *counter, int member)
    >                return &counter->limit;
    >        case RES_FAILCNT:
    >                return &counter->failcnt;
    > +       case RES_THRESHOLD:
    > +               return &counter->threshold;
    >        };
    >
    >        BUG();
    > --
    > 1.5.6.3
    >
    >
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