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    SubjectRe: [PATCH 1/2] Resource usage threshold notification addition to res_counter (v3)
    On Mon, 13 Jul 2009 17:36:40 -0700
    Paul Menage <menage@google.com> wrote:

    > 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.
    >
    Ah, Hmm...maybe yes.

    But the problem is "hierarchy". (even if this usage notifier don't handle it.)

    While we charge as following res_coutner+hierarchy

    res_counter_A + PAGE_SIZE
    res_counter_B + PAGE_SIZE
    res_counter_C + PAGE_SIZE

    Checking "where we exceeds" in smart way is not very easy. Balbir's soft limit does
    similar check but it's not very smart, either I think.

    If there are prural thesholds (notifer, softlimit, etc...), this is worth to be
    tried. Hmm...if not, size of res_coutner excees 128bytes and we'll see terrible counter.
    Any idea ?

    Thanks,
    -Kame


    > 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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