Messages in this thread Patch in this message | | | Date | Fri, 13 Jun 2008 18:29:24 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | [PATCH 1/6] res_counter: handle limit change |
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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; + /* * 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
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