Re: [PATCH 1/2] Resource usage threshold notification addition to res_counter (v3)

[Paul Menage <menage@google.com>]

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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