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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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