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SubjectRe: [PATCH RFC v0 2/3] res_counter: implement thresholds
Hi.

On Thu, 26 Nov 2009 19:11:16 +0200, "Kirill A. Shutemov" <kirill@shutemov.name> wrote:
> It allows to setup two thresholds: one above current usage and one
> below. Callback threshold_notifier() will be called if a threshold is
> crossed.
>
> Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
> ---
> include/linux/res_counter.h | 44 +++++++++++++++++++++++++++++++++++++++++++
> kernel/res_counter.c | 4 +++
> 2 files changed, 48 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/res_counter.h b/include/linux/res_counter.h
> index fcb9884..bca99a5 100644
> --- a/include/linux/res_counter.h
> +++ b/include/linux/res_counter.h
> @@ -9,6 +9,10 @@
> *
> * Author: Pavel Emelianov <xemul@openvz.org>
> *
> + * Thresholds support
> + * Copyright (C) 2009 Nokia Corporation
> + * Author: Kirill A. Shutemov
> + *
> * See Documentation/cgroups/resource_counter.txt for more
> * info about what this counter is.
> */
> @@ -42,6 +46,13 @@ struct res_counter {
> * the number of unsuccessful attempts to consume the resource
> */
> unsigned long long failcnt;
> +
> + unsigned long long threshold_above;
> + unsigned long long threshold_below;
> + void (*threshold_notifier)(struct res_counter *counter,
> + unsigned long long usage,
> + unsigned long long threshold);
> +
> /*
> * the lock to protect all of the above.
> * the routines below consider this to be IRQ-safe
> @@ -145,6 +156,20 @@ static inline bool res_counter_soft_limit_check_locked(struct res_counter *cnt)
> return false;
> }
>
> +static inline void res_counter_threshold_notify_locked(struct res_counter *cnt)
> +{
> + if (cnt->usage >= cnt->threshold_above) {
> + cnt->threshold_notifier(cnt, cnt->usage, cnt->threshold_above);
> + return;
> + }
> +
> + if (cnt->usage < cnt->threshold_below) {
> + cnt->threshold_notifier(cnt, cnt->usage, cnt->threshold_below);
> + return;
> + }
> +}
> +
> +
> /**
> * Get the difference between the usage and the soft limit
> * @cnt: The counter
> @@ -238,4 +263,23 @@ res_counter_set_soft_limit(struct res_counter *cnt,
> return 0;
> }
>
> +static inline int
> +res_counter_set_thresholds(struct res_counter *cnt,
> + unsigned long long threshold_above,
> + unsigned long long threshold_below)
> +{
> + unsigned long flags;
> + int ret = -EINVAL;
> +
> + spin_lock_irqsave(&cnt->lock, flags);
> + if ((cnt->usage < threshold_above) &&
> + (cnt->usage >= threshold_below)) {
> + cnt->threshold_above = threshold_above;
> + cnt->threshold_below = threshold_below;
> + ret = 0;
> + }
> + spin_unlock_irqrestore(&cnt->lock, flags);
> + return ret;
> +}
> +
> #endif
> diff --git a/kernel/res_counter.c b/kernel/res_counter.c
> index bcdabf3..646c29c 100644
> --- a/kernel/res_counter.c
> +++ b/kernel/res_counter.c
> @@ -20,6 +20,8 @@ void res_counter_init(struct res_counter *counter, struct res_counter *parent)
> spin_lock_init(&counter->lock);
> counter->limit = RESOURCE_MAX;
> counter->soft_limit = RESOURCE_MAX;
> + counter->threshold_above = RESOURCE_MAX;
> + counter->threshold_below = 0ULL;
> counter->parent = parent;
> }
>
> @@ -33,6 +35,7 @@ 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;
> }
>
> @@ -73,6 +76,7 @@ void res_counter_uncharge_locked(struct res_counter *counter, unsigned long val)
> val = counter->usage;
>
> counter->usage -= val;
> + res_counter_threshold_notify_locked(counter);
> }
>
hmm.. this adds new checks to hot-path of process life cycle.

Do you have any number on performance impact of these patches(w/o setting any threshold)?
IMHO, it might be small enough to be ignored because KAMEZAWA-san's coalesce charge/uncharge
patches have decreased charge/uncharge for res_counter itself, but I want to know just to make sure.


Regards,
Daisuke Nishimura.


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