On Mon, 29 Nov 2010 22:49:43 -0800
Ying Han <yinghan@xxxxxxxxxx> wrote:
> The per cgroup kswapd is invoked at mem_cgroup_charge when the cgroup's memory
> usage above a threshold--low_wmark. Then the kswapd thread starts to reclaim
> pages in a priority loop similar to global algorithm. The kswapd is done if the
> memory usage below a threshold--high_wmark.
>
> The per cgroup background reclaim is based on the per cgroup LRU and also adds
> per cgroup watermarks. There are two watermarks including "low_wmark" and
> "high_wmark", and they are calculated based on the limit_in_bytes(hard_limit)
> for each cgroup. Each time the hard_limit is change, the corresponding wmarks
> are re-calculated. Since memory controller charges only user pages, there is
> no need for a "min_wmark". The current calculation of wmarks is a function of
> "memory.min_free_kbytes" which could be adjusted by writing different values
> into the new api. This is added mainly for debugging purpose.
>
> Signed-off-by: Ying Han <yinghan@xxxxxxxxxx>
A few points.
1. I can understand the motivation for including low/high watermark to
res_coutner. But, sadly, compareing all charge will make the counter slow.
IMHO, as memory controller threshold-check or soft limit, checking usage
periodically based on event counter is enough. It will be low cost.
2. min_free_kbytes must be automatically calculated.
For example, max(3% of limit, 20MB) or some.
3. When you allow min_free_kbytes to be set by users, please compare
it with the limit.
I think min_free_kbyte interface itself should be in another patch...
interface code tends to make patch bigger.
> ---
> include/linux/memcontrol.h | 1 +
> include/linux/res_counter.h | 88 ++++++++++++++++++++++++++++++-
> kernel/res_counter.c | 26 ++++++++--
> mm/memcontrol.c | 123 +++++++++++++++++++++++++++++++++++++++++--
> mm/vmscan.c | 10 ++++
> 5 files changed, 238 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 159a076..90fe7fe 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -76,6 +76,7 @@ int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem);
>
> extern struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page);
> extern struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p);
> +extern int mem_cgroup_watermark_ok(struct mem_cgroup *mem, int charge_flags);
>
> static inline
> int mm_match_cgroup(const struct mm_struct *mm, const struct mem_cgroup *cgroup)
> diff --git a/include/linux/res_counter.h b/include/linux/res_counter.h
> index fcb9884..eed12c5 100644
> --- a/include/linux/res_counter.h
> +++ b/include/linux/res_counter.h
> @@ -39,6 +39,16 @@ struct res_counter {
> */
> unsigned long long soft_limit;
> /*
> + * the limit that reclaim triggers. TODO: res_counter in mem
> + * or wmark_limit.
> + */
> + unsigned long long low_wmark_limit;
> + /*
> + * the limit that reclaim stops. TODO: res_counter in mem or
> + * wmark_limit.
> + */
> + unsigned long long high_wmark_limit;
> + /*
> * the number of unsuccessful attempts to consume the resource
> */
> unsigned long long failcnt;
> @@ -55,6 +65,10 @@ struct res_counter {
>
> #define RESOURCE_MAX (unsigned long long)LLONG_MAX
>
> +#define CHARGE_WMARK_MIN 0x01
> +#define CHARGE_WMARK_LOW 0x02
> +#define CHARGE_WMARK_HIGH 0x04
> +
> /**
> * Helpers to interact with userspace
> * res_counter_read_u64() - returns the value of the specified member.
> @@ -92,6 +106,8 @@ enum {
> RES_LIMIT,
> RES_FAILCNT,
> RES_SOFT_LIMIT,
> + RES_LOW_WMARK_LIMIT,
> + RES_HIGH_WMARK_LIMIT
> };
>
> /*
> @@ -112,9 +128,10 @@ void res_counter_init(struct res_counter *counter, struct res_counter *parent);
> */
>
> int __must_check res_counter_charge_locked(struct res_counter *counter,
> - unsigned long val);
> + unsigned long val, int charge_flags);
> int __must_check res_counter_charge(struct res_counter *counter,
> - unsigned long val, struct res_counter **limit_fail_at);
> + unsigned long val, int charge_flags,
> + struct res_counter **limit_fail_at);
>
> /*
> * uncharge - tell that some portion of the resource is released
> @@ -145,6 +162,24 @@ static inline bool res_counter_soft_limit_check_locked(struct res_counter *cnt)
> return false;
> }
>
> +static inline bool
> +res_counter_high_wmark_limit_check_locked(struct res_counter *cnt)
> +{
> + if (cnt->usage < cnt->high_wmark_limit)
> + return true;
> +
> + return false;
> +}
> +
> +static inline bool
> +res_counter_low_wmark_limit_check_locked(struct res_counter *cnt)
> +{
> + if (cnt->usage < cnt->low_wmark_limit)
> + return true;
> +
> + return false;
> +}
> +
> /**
> * Get the difference between the usage and the soft limit
> * @cnt: The counter
> @@ -193,6 +228,30 @@ static inline bool res_counter_check_under_soft_limit(struct res_counter *cnt)
> return ret;
> }
>
> +static inline bool
> +res_counter_check_under_low_wmark_limit(struct res_counter *cnt)
> +{
> + bool ret;
> + unsigned long flags;
> +
> + spin_lock_irqsave(&cnt->lock, flags);
> + ret = res_counter_low_wmark_limit_check_locked(cnt);
> + spin_unlock_irqrestore(&cnt->lock, flags);
> + return ret;
> +}
> +
> +static inline bool
> +res_counter_check_under_high_wmark_limit(struct res_counter *cnt)
> +{
> + bool ret;
> + unsigned long flags;
> +
> + spin_lock_irqsave(&cnt->lock, flags);
> + ret = res_counter_high_wmark_limit_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;
> @@ -220,6 +279,8 @@ static inline int res_counter_set_limit(struct res_counter *cnt,
> spin_lock_irqsave(&cnt->lock, flags);
> if (cnt->usage <= limit) {
> cnt->limit = limit;
> + cnt->low_wmark_limit = limit;
> + cnt->high_wmark_limit = limit;
> ret = 0;
> }
> spin_unlock_irqrestore(&cnt->lock, flags);
> @@ -238,4 +299,27 @@ res_counter_set_soft_limit(struct res_counter *cnt,
> return 0;
> }
>
> +static inline int
> +res_counter_set_high_wmark_limit(struct res_counter *cnt,
> + unsigned long long wmark_limit)
> +{
> + unsigned long flags;
> +
> + spin_lock_irqsave(&cnt->lock, flags);
> + cnt->high_wmark_limit = wmark_limit;
> + spin_unlock_irqrestore(&cnt->lock, flags);
> + return 0;
> +}
> +
> +static inline int
> +res_counter_set_low_wmark_limit(struct res_counter *cnt,
> + unsigned long long wmark_limit)
> +{
> + unsigned long flags;
> +
> + spin_lock_irqsave(&cnt->lock, flags);
> + cnt->low_wmark_limit = wmark_limit;
> + spin_unlock_irqrestore(&cnt->lock, flags);
> + return 0;
> +}
> #endif
> diff --git a/kernel/res_counter.c b/kernel/res_counter.c
> index c7eaa37..a524349 100644
> --- a/kernel/res_counter.c
> +++ b/kernel/res_counter.c
> @@ -19,12 +19,26 @@ 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->low_wmark_limit = RESOURCE_MAX;
> + counter->high_wmark_limit = RESOURCE_MAX;
> counter->parent = parent;
> }
>
> -int res_counter_charge_locked(struct res_counter *counter, unsigned long val)
> +int res_counter_charge_locked(struct res_counter *counter, unsigned long val,
> + int charge_flags)
> {
> - if (counter->usage + val > counter->limit) {
> + unsigned long long limit = 0;
> +
> + if (charge_flags & CHARGE_WMARK_LOW)
> + limit = counter->low_wmark_limit;
> +
> + if (charge_flags & CHARGE_WMARK_HIGH)
> + limit = counter->high_wmark_limit;
> +
> + if (charge_flags & CHARGE_WMARK_MIN)
> + limit = counter->limit;
> +
> + if (counter->usage + val > limit) {
> counter->failcnt++;
> return -ENOMEM;
> }
> @@ -36,7 +50,7 @@ int res_counter_charge_locked(struct res_counter *counter, unsigned long val)
> }
>
> int res_counter_charge(struct res_counter *counter, unsigned long val,
> - struct res_counter **limit_fail_at)
> + int charge_flags, struct res_counter **limit_fail_at)
> {
> int ret;
> unsigned long flags;
> @@ -46,7 +60,7 @@ int res_counter_charge(struct res_counter *counter, unsigned long val,
> local_irq_save(flags);
> for (c = counter; c != NULL; c = c->parent) {
> spin_lock(&c->lock);
> - ret = res_counter_charge_locked(c, val);
> + ret = res_counter_charge_locked(c, val, charge_flags);
> spin_unlock(&c->lock);
> if (ret < 0) {
> *limit_fail_at = c;
> @@ -103,6 +117,10 @@ res_counter_member(struct res_counter *counter, int member)
> return &counter->failcnt;
> case RES_SOFT_LIMIT:
> return &counter->soft_limit;
> + case RES_LOW_WMARK_LIMIT:
> + return &counter->low_wmark_limit;
> + case RES_HIGH_WMARK_LIMIT:
> + return &counter->high_wmark_limit;
> };
>
> BUG();
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index dca3590..a0c6ed9 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -265,6 +265,7 @@ struct mem_cgroup {
> spinlock_t pcp_counter_lock;
>
> wait_queue_head_t *kswapd_wait;
> + unsigned long min_free_kbytes;
> };
>
> /* Stuffs for move charges at task migration. */
> @@ -370,6 +371,7 @@ static void mem_cgroup_get(struct mem_cgroup *mem);
> static void mem_cgroup_put(struct mem_cgroup *mem);
> static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem);
> static void drain_all_stock_async(void);
> +static unsigned long get_min_free_kbytes(struct mem_cgroup *mem);
>
> static struct mem_cgroup_per_zone *
> mem_cgroup_zoneinfo(struct mem_cgroup *mem, int nid, int zid)
> @@ -796,6 +798,32 @@ static inline bool mem_cgroup_is_root(struct mem_cgroup *mem)
> return (mem == root_mem_cgroup);
> }
>
> +void setup_per_memcg_wmarks(struct mem_cgroup *mem)
> +{
> + u64 limit;
> + unsigned long min_free_kbytes;
> +
> + min_free_kbytes = get_min_free_kbytes(mem);
> + limit = mem_cgroup_get_limit(mem);
> + if (min_free_kbytes == 0) {
> + res_counter_set_low_wmark_limit(&mem->res, limit);
> + res_counter_set_high_wmark_limit(&mem->res, limit);
> + } else {
> + unsigned long page_min = min_free_kbytes >> (PAGE_SHIFT - 10);
> + unsigned long lowmem_pages = 2048;
> + unsigned long low_wmark, high_wmark;
> + u64 tmp;
> +
> + tmp = (u64)page_min * limit;
> + do_div(tmp, lowmem_pages);
> +
> + low_wmark = tmp + (tmp >> 1);
> + high_wmark = tmp + (tmp >> 2);
> + res_counter_set_low_wmark_limit(&mem->res, low_wmark);
> + res_counter_set_high_wmark_limit(&mem->res, high_wmark);
> + }
> +}
> +
> /*
> * Following LRU functions are allowed to be used without PCG_LOCK.
> * Operations are called by routine of global LRU independently from memcg.
> @@ -1148,6 +1176,22 @@ static unsigned int get_swappiness(struct mem_cgroup *memcg)
> return swappiness;
> }
>
> +static unsigned long get_min_free_kbytes(struct mem_cgroup *memcg)
> +{
> + struct cgroup *cgrp = memcg->css.cgroup;
> + unsigned long min_free_kbytes;
> +
> + /* root ? */
> + if (cgrp == NULL || cgrp->parent == NULL)
> + return 0;
> +
> + spin_lock(&memcg->reclaim_param_lock);
> + min_free_kbytes = memcg->min_free_kbytes;
> + spin_unlock(&memcg->reclaim_param_lock);
> +
> + return min_free_kbytes;
> +}
> +
> static void mem_cgroup_start_move(struct mem_cgroup *mem)
> {
> int cpu;
> @@ -1844,12 +1888,13 @@ static int __mem_cgroup_do_charge(struct mem_cgroup *mem, gfp_t gfp_mask,
> unsigned long flags = 0;
> int ret;
>
> - ret = res_counter_charge(&mem->res, csize, &fail_res);
> + ret = res_counter_charge(&mem->res, csize, CHARGE_WMARK_MIN, &fail_res);
>
> if (likely(!ret)) {
> if (!do_swap_account)
> return CHARGE_OK;
> - ret = res_counter_charge(&mem->memsw, csize, &fail_res);
> + ret = res_counter_charge(&mem->memsw, csize, CHARGE_WMARK_MIN,
> + &fail_res);
> if (likely(!ret))
> return CHARGE_OK;
>
> @@ -3733,6 +3778,37 @@ static int mem_cgroup_swappiness_write(struct cgroup *cgrp, struct cftype *cft,
> return 0;
> }
>
> +static u64 mem_cgroup_min_free_read(struct cgroup *cgrp, struct cftype *cft)
> +{
> + struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
> +
> + return get_min_free_kbytes(memcg);
> +}
> +
> +static int mem_cgroup_min_free_write(struct cgroup *cgrp, struct cftype *cfg,
> + u64 val)
> +{
> + struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
> + struct mem_cgroup *parent;
> +
> + if (cgrp->parent == NULL)
> + return -EINVAL;
> +
> + parent = mem_cgroup_from_cont(cgrp->parent);
> +
> + cgroup_lock();
> +
> + spin_lock(&memcg->reclaim_param_lock);
> + memcg->min_free_kbytes = val;
> + spin_unlock(&memcg->reclaim_param_lock);
> +
> + cgroup_unlock();
Why cgroup_lock is required ?
Thanks,
-Kame
> +
> + setup_per_memcg_wmarks(memcg);
> + return 0;
> +
> +}
> +
> static void __mem_cgroup_threshold(struct mem_cgroup *memcg, bool swap)
> {
> struct mem_cgroup_threshold_ary *t;
> @@ -4024,6 +4100,21 @@ static void mem_cgroup_oom_unregister_event(struct cgroup *cgrp,
> mutex_unlock(&memcg_oom_mutex);
> }
>
> +static int mem_cgroup_wmark_read(struct cgroup *cgrp,
> + struct cftype *cft, struct cgroup_map_cb *cb)
> +{
> + struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
> + unsigned long low_wmark, high_wmark;
> +
> + low_wmark = res_counter_read_u64(&mem->res, RES_LOW_WMARK_LIMIT);
> + high_wmark = res_counter_read_u64(&mem->res, RES_HIGH_WMARK_LIMIT);
> +
> + cb->fill(cb, "memcg_low_wmark", low_wmark);
> + cb->fill(cb, "memcg_high_wmark", high_wmark);
> +
> + return 0;
> +}
> +
> static int mem_cgroup_oom_control_read(struct cgroup *cgrp,
> struct cftype *cft, struct cgroup_map_cb *cb)
> {
> @@ -4127,6 +4218,15 @@ static struct cftype mem_cgroup_files[] = {
> .unregister_event = mem_cgroup_oom_unregister_event,
> .private = MEMFILE_PRIVATE(_OOM_TYPE, OOM_CONTROL),
> },
> + {
> + .name = "min_free_kbytes",
> + .write_u64 = mem_cgroup_min_free_write,
> + .read_u64 = mem_cgroup_min_free_read,
> + },
> + {
> + .name = "reclaim_wmarks",
> + .read_map = mem_cgroup_wmark_read,
> + },
> };
>
> #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
> @@ -4308,6 +4408,19 @@ static void __init enable_swap_cgroup(void)
> }
> #endif
>
> +int mem_cgroup_watermark_ok(struct mem_cgroup *mem,
> + int charge_flags)
> +{
> + long ret = 0;
> +
> + if (charge_flags & CHARGE_WMARK_LOW)
> + ret = res_counter_check_under_low_wmark_limit(&mem->res);
> + if (charge_flags & CHARGE_WMARK_HIGH)
> + ret = res_counter_check_under_high_wmark_limit(&mem->res);
> +
> + return ret;
> +}
> +
> static int mem_cgroup_soft_limit_tree_init(void)
> {
> struct mem_cgroup_tree_per_node *rtpn;
> @@ -4450,10 +4563,12 @@ static int mem_cgroup_do_precharge(unsigned long count)
> * are still under the same cgroup_mutex. So we can postpone
> * css_get().
> */
> - if (res_counter_charge(&mem->res, PAGE_SIZE * count, &dummy))
> + if (res_counter_charge(&mem->res, PAGE_SIZE * count,
> + CHARGE_WMARK_MIN, &dummy))
> goto one_by_one;
> if (do_swap_account && res_counter_charge(&mem->memsw,
> - PAGE_SIZE * count, &dummy)) {
> + PAGE_SIZE * count,
> + CHARGE_WMARK_MIN, &dummy)) {
> res_counter_uncharge(&mem->res, PAGE_SIZE * count);
> goto one_by_one;
> }
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index e08005e..6d5702b 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -46,6 +46,8 @@
>
> #include <linux/swapops.h>
>
> +#include <linux/res_counter.h>
> +
> #include "internal.h"
>
> #define CREATE_TRACE_POINTS
> @@ -2127,11 +2129,19 @@ static int sleeping_prematurely(struct kswapd *kswapd, int order,
> {
> int i;
> pg_data_t *pgdat = kswapd->kswapd_pgdat;
> + struct mem_cgroup *mem = kswapd->kswapd_mem;
>
> /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
> if (remaining)
> return 1;
>
> + if (mem) {
> + if (!mem_cgroup_watermark_ok(kswapd->kswapd_mem,
> + CHARGE_WMARK_HIGH))
> + return 1;
> + return 0;
> + }
> +
> /* If after HZ/10, a zone is below the high mark, it's premature */
> for (i = 0; i < pgdat->nr_zones; i++) {
> struct zone *zone = pgdat->node_zones + i;
> --
> 1.7.3.1
>
>
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