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SubjectRe: [PATCH 1/2] Resource usage threshold notification addition to res_counter (v3)
On Mon, 13 Jul 2009 17:16:20 -0700
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.
> +

This interface isn't very useful..hard to use..can't you just return the result as
"exceeds threshold" to the callers ?

If I was you, I'll add following state to res_counter

enum {
RES_BELOW_THRESH,
RES_OVER_THRESH,
} res_state;
struct res_counter {
.....
enum res_state state;
}
Then, caller does
example)
prev_state = res->state;
res_counter_charge(res....)
if (prev_state != res->state)
do_xxxxx..
notifier under spinlock is not usual interface. And if this is "notifier",
something generic, notifier_call_chain should be used rather than original
one, IIUC.

So, avoiding to use "callback" is a way to go, I think.

Thanks,
-Kame




> + 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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