[Devel] Re: [PATCH 1/2] Resource usage threshold notification addition to res_counter (v3)
KAMEZAWA Hiroyuki
kamezawa.hiroyu at jp.fujitsu.com
Mon Jul 13 17:47:29 PDT 2009
On Mon, 13 Jul 2009 17:36:40 -0700
Paul Menage <menage at 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 at embeddedalley.com> wrote:
> > This patch updates the Resource Counter to add a configurable resource usage
> > threshold notification mechanism.
> >
> > Signed-off-by: Vladislav Buzov <vbuzov at embeddedalley.com>
> > Signed-off-by: Dan Malek <dan at 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 at openvz.org>
> > *
> > + * Resouce usage threshold notification update
> > + * Copyright 2009 CE Linux Forum and Embedded Alley Solutions, Inc.
> > + * Author: Dan Malek <dan at embeddedalley.com>
> > + * Author: Vladislav Buzov <vbuzov at 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 at openvz.org>
> > *
> > + * Resouce usage threshold notification update
> > + * Copyright 2009 CE Linux Forum and Embedded Alley Solutions, Inc.
> > + * Author: Dan Malek <dan at embeddedalley.com>
> > + * Author: Vladislav Buzov <vbuzov at 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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