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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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