lkml.org 
[lkml]   [2008]   [Jun]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/6] res_counter: handle limit change
KAMEZAWA Hiroyuki wrote:
> Add a support to shrink_usage_at_limit_change feature to res_counter.
> memcg will use this to drop pages.
>
> Change log: xxx -> v4 (new file.)
> - cut out the limit-change part from hierarchy patch set.
> - add "retry_count" arguments to shrink_usage(). This allows that we don't
> have to set the default retry loop count.
> - res_counter_check_under_val() is added to support subsystem.
> - res_counter_init() is res_counter_init_ops(cnt, NULL)
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>
> ---
> Documentation/controllers/resource_counter.txt | 19 +++++-
> include/linux/res_counter.h | 33 ++++++++++-
> kernel/res_counter.c | 74 ++++++++++++++++++++++++-
> 3 files changed, 121 insertions(+), 5 deletions(-)
>
> Index: linux-2.6.26-rc5-mm3/include/linux/res_counter.h
> ===================================================================
> --- linux-2.6.26-rc5-mm3.orig/include/linux/res_counter.h
> +++ linux-2.6.26-rc5-mm3/include/linux/res_counter.h
> @@ -21,6 +21,13 @@
> * the helpers described beyond
> */
>
> +struct res_counter;
> +struct res_counter_ops {
> + /* called when the subsystem has to reduce the usage. */
> + int (*shrink_usage)(struct res_counter *cnt, unsigned long long val,
> + int retry_count);
> +};
> +
> struct res_counter {
> /*
> * the current resource consumption level
> @@ -39,6 +46,10 @@ struct res_counter {
> */
> unsigned long long failcnt;
> /*
> + * registered callbacks etc...for res_counter.
> + */
> + struct res_counter_ops ops;
> + /*

Why would we need such? All res_counter.limit update comes via the appropiate
cgroup's files, so it can do whatever it needs w/o any callbacks?

And (if we definitely need one) isn't it better to make it a
struct res_counter_ops *ops;
pointer?

> * the lock to protect all of the above.
> * the routines below consider this to be IRQ-safe
> */
> @@ -82,7 +93,13 @@ enum {
> * helpers for accounting
> */
>
> -void res_counter_init(struct res_counter *counter);
> +void res_counter_init_ops(struct res_counter *counter,
> + struct res_counter_ops *ops);
> +
> +static inline void res_counter_init(struct res_counter *counter)
> +{
> + res_counter_init_ops(counter, NULL);
> +}
>
> /*
> * charge - try to consume more resource.
> @@ -136,6 +153,20 @@ static inline bool res_counter_check_und
> return ret;
> }
>
> +static inline bool res_counter_check_under_val(struct res_counter *cnt,
> + unsigned long long val)
> +{
> + bool ret = false;
> + unsigned long flags;
> +
> + spin_lock_irqsave(&cnt->lock, flags);
> + if (cnt->usage <= val)
> + ret = true;
> + spin_unlock_irqrestore(&cnt->lock, flags);
> +
> + return ret;
> +}
> +
> static inline void res_counter_reset_max(struct res_counter *cnt)
> {
> unsigned long flags;
> Index: linux-2.6.26-rc5-mm3/kernel/res_counter.c
> ===================================================================
> --- linux-2.6.26-rc5-mm3.orig/kernel/res_counter.c
> +++ linux-2.6.26-rc5-mm3/kernel/res_counter.c
> @@ -14,10 +14,22 @@
> #include <linux/res_counter.h>
> #include <linux/uaccess.h>
>
> -void res_counter_init(struct res_counter *counter)
> +/**
> + * res_counter_init_ops -- initialize res_counter.
> + * @counter: the res_counter to be initialized
> + * @ops: the res_counter_ops for this res_counter. This argument can be NULL
> + * and is copied.
> + *
> + * init spinlock and set limit to be very very big value.
> + */
> +
> +void res_counter_init_ops(struct res_counter *counter,
> + struct res_counter_ops *ops)
> {
> spin_lock_init(&counter->lock);
> counter->limit = (unsigned long long)LLONG_MAX;
> + if (ops)
> + counter->ops = *ops;
> }
>
> int res_counter_charge_locked(struct res_counter *counter, unsigned long val)
> @@ -102,6 +114,46 @@ u64 res_counter_read_u64(struct res_coun
> return *res_counter_member(counter, member);
> }
>
> +/*
> + * Called when the limit changes if res_counter has ops->shrink_usage.
> + * This function uses shrink usage to below new limit. returns 0 at success.
> + */
> +
> +static int res_counter_resize_limit(struct res_counter *cnt,
> + unsigned long long val)
> +{
> + int retry_count = 0;
> + int ret = -EBUSY;
> + unsigned long flags;
> +
> + BUG_ON(!cnt->ops.shrink_usage);
> + while (1) {
> + spin_lock_irqsave(&cnt->lock, flags);
> + if (cnt->usage <= val) {
> + cnt->limit = val;
> + ret = 0;
> + spin_unlock_irqrestore(&cnt->lock, flags);
> + break;
> + }
> + BUG_ON(val > cnt->limit);
> + spin_unlock_irqrestore(&cnt->lock, flags);
> +
> + /*
> + * Rest before calling callback().... rest after callback
> + * tends to add difference between the result of callback and
> + * the check in next loop.
> + */
> + cond_resched();
> +
> + ret = cnt->ops.shrink_usage(cnt, val, retry_count);
> + if (!ret)
> + break;
> + retry_count++;
> + }
> + return ret;
> +}
> +
> +
> ssize_t res_counter_write(struct res_counter *counter, int member,
> const char __user *userbuf, size_t nbytes, loff_t *pos,
> int (*write_strategy)(char *st_buf, unsigned long long *val))
> @@ -133,11 +185,29 @@ ssize_t res_counter_write(struct res_cou
> if (*end != '\0')
> goto out_free;
> }
> + switch (member) {
> + case RES_LIMIT:
> + if (counter->ops.shrink_usage) {
> + ret = res_counter_resize_limit(counter, tmp);
> + goto done;
> + }
> + break;
> + default:
> + /*
> + * Considering future implementation, we'll have to handle
> + * other members and "fallback" will not work well. So, we
> + * avoid to make use of "default" here.
> + */
> + break;
> + }
> spin_lock_irqsave(&counter->lock, flags);
> val = res_counter_member(counter, member);
> *val = tmp;
> spin_unlock_irqrestore(&counter->lock, flags);
> - ret = nbytes;
> + ret = 0;
> +done:
> + if (!ret)
> + ret = nbytes;
> out_free:
> kfree(buf);
> out:
> Index: linux-2.6.26-rc5-mm3/Documentation/controllers/resource_counter.txt
> ===================================================================
> --- linux-2.6.26-rc5-mm3.orig/Documentation/controllers/resource_counter.txt
> +++ linux-2.6.26-rc5-mm3/Documentation/controllers/resource_counter.txt
> @@ -39,7 +39,11 @@ 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. res_counter_ops.
> + Callbacks for helping resource_counter per each subsystem.
> + - shrink_usage() .... called at limit change (decrease).
> +
> + f. spinlock_t lock
>
> Protects changes of the above values.
>
> @@ -141,8 +145,19 @@ counter fields. They are recommended to
> failcnt reset to zero
>
>
> +5. res_counter_ops (Callbacks)
>
> -5. Usage example
> + res_counter_ops is for implementing feedback control from res_counter
> + to subsystem. Each one has each own purpose and the subsystem doesn't
> + necessary to provide all callbacks. Just implement necessary ones.
> +
> + - shrink_usage(res_counter, newlimit, retry)
> + Called for reducing usage to newlimit, retry is incremented per
> + loop. (See memory resource controller as example.)
> + Returns 0 at success. Any error code is acceptable but -EBUSY will be
> + suitable to show "the kernel can't shrink usage."
> +
> +6. Usage example
>
> a. Declare a task group (take a look at cgroups subsystem for this) and
> fold a res_counter into it
>
>



\
 
 \ /
  Last update: 2008-06-16 08:47    [W:0.983 / U:1.036 seconds]
©2003-2014 Jasper Spaans. Advertise on this site