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SubjectRe: [PATCH -mmotm 2/3] memcg: dirty pages accounting and limiting infrastructure
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On Mon, Mar 1, 2010 at 11:23 PM, Andrea Righi <arighi@develer.com> wrote:
> Infrastructure to account dirty pages per cgroup and add dirty limit
> interfaces in the cgroupfs:
>
>  - Direct write-out: memory.dirty_ratio, memory.dirty_bytes
>
>  - Background write-out: memory.dirty_background_ratio, memory.dirty_background_bytes
>
> Signed-off-by: Andrea Righi <arighi@develer.com>
> ---
>  include/linux/memcontrol.h |   77 ++++++++++-
>  mm/memcontrol.c            |  336 ++++++++++++++++++++++++++++++++++++++++----
>  2 files changed, 384 insertions(+), 29 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 1f9b119..cc88b2e 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -19,12 +19,50 @@
>
>  #ifndef _LINUX_MEMCONTROL_H
>  #define _LINUX_MEMCONTROL_H
> +
> +#include <linux/writeback.h>
>  #include <linux/cgroup.h>
> +
>  struct mem_cgroup;
>  struct page_cgroup;
>  struct page;
>  struct mm_struct;
>
> +/* Cgroup memory statistics items exported to the kernel */
> +enum mem_cgroup_page_stat_item {
> +       MEMCG_NR_DIRTYABLE_PAGES,
> +       MEMCG_NR_RECLAIM_PAGES,
> +       MEMCG_NR_WRITEBACK,
> +       MEMCG_NR_DIRTY_WRITEBACK_PAGES,
> +};
> +
> +/*
> + * Statistics for memory cgroup.
> + */
> +enum mem_cgroup_stat_index {
> +       /*
> +        * For MEM_CONTAINER_TYPE_ALL, usage = pagecache + rss.
> +        */
> +       MEM_CGROUP_STAT_CACHE,     /* # of pages charged as cache */
> +       MEM_CGROUP_STAT_RSS,       /* # of pages charged as anon rss */
> +       MEM_CGROUP_STAT_FILE_MAPPED,  /* # of pages charged as file rss */
> +       MEM_CGROUP_STAT_PGPGIN_COUNT,   /* # of pages paged in */
> +       MEM_CGROUP_STAT_PGPGOUT_COUNT,  /* # of pages paged out */
> +       MEM_CGROUP_STAT_EVENTS, /* sum of pagein + pageout for internal use */
> +       MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
> +       MEM_CGROUP_STAT_SOFTLIMIT, /* decrements on each page in/out.
> +                                       used by soft limit implementation */
> +       MEM_CGROUP_STAT_THRESHOLDS, /* decrements on each page in/out.
> +                                       used by threshold implementation */
> +       MEM_CGROUP_STAT_FILE_DIRTY,   /* # of dirty pages in page cache */
> +       MEM_CGROUP_STAT_WRITEBACK,   /* # of pages under writeback */
> +       MEM_CGROUP_STAT_WRITEBACK_TEMP,   /* # of pages under writeback using
> +                                               temporary buffers */
> +       MEM_CGROUP_STAT_UNSTABLE_NFS,   /* # of NFS unstable pages */
> +
> +       MEM_CGROUP_STAT_NSTATS,
> +};
> +
>  #ifdef CONFIG_CGROUP_MEM_RES_CTLR
>  /*
>  * All "charge" functions with gfp_mask should use GFP_KERNEL or
> @@ -117,6 +155,13 @@ extern void mem_cgroup_print_oom_info(struct mem_cgroup *memcg,
>  extern int do_swap_account;
>  #endif
>
> +extern long mem_cgroup_dirty_ratio(void);
> +extern unsigned long mem_cgroup_dirty_bytes(void);
> +extern long mem_cgroup_dirty_background_ratio(void);
> +extern unsigned long mem_cgroup_dirty_background_bytes(void);
> +
> +extern s64 mem_cgroup_page_stat(enum mem_cgroup_page_stat_item item);
> +
>  static inline bool mem_cgroup_disabled(void)
>  {
>        if (mem_cgroup_subsys.disabled)
> @@ -125,7 +170,8 @@ static inline bool mem_cgroup_disabled(void)
>  }
>
>  extern bool mem_cgroup_oom_called(struct task_struct *task);
> -void mem_cgroup_update_file_mapped(struct page *page, int val);
> +void mem_cgroup_update_stat(struct page *page,
> +                       enum mem_cgroup_stat_index idx, int val);
>  unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
>                                                gfp_t gfp_mask, int nid,
>                                                int zid);
> @@ -300,8 +346,8 @@ mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
>  {
>  }
>
> -static inline void mem_cgroup_update_file_mapped(struct page *page,
> -                                                       int val)
> +static inline void mem_cgroup_update_stat(struct page *page,
> +                       enum mem_cgroup_stat_index idx, int val)
>  {
>  }
>
> @@ -312,6 +358,31 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
>        return 0;
>  }
>
> +static inline long mem_cgroup_dirty_ratio(void)
> +{
> +       return vm_dirty_ratio;
> +}
> +
> +static inline unsigned long mem_cgroup_dirty_bytes(void)
> +{
> +       return vm_dirty_bytes;
> +}
> +
> +static inline long mem_cgroup_dirty_background_ratio(void)
> +{
> +       return dirty_background_ratio;
> +}
> +
> +static inline unsigned long mem_cgroup_dirty_background_bytes(void)
> +{
> +       return dirty_background_bytes;
> +}
> +
> +static inline s64 mem_cgroup_page_stat(enum mem_cgroup_page_stat_item item)
> +{
> +       return -ENOMEM;

Why ENOMEM? Probably, EINVAL or ENOSYS?

> +}
> +
>  #endif /* CONFIG_CGROUP_MEM_CONT */
>
>  #endif /* _LINUX_MEMCONTROL_H */
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index a443c30..e74cf66 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -66,31 +66,16 @@ static int really_do_swap_account __initdata = 1; /* for remember boot option*/
>  #define SOFTLIMIT_EVENTS_THRESH (1000)
>  #define THRESHOLDS_EVENTS_THRESH (100)
>
> -/*
> - * Statistics for memory cgroup.
> - */
> -enum mem_cgroup_stat_index {
> -       /*
> -        * For MEM_CONTAINER_TYPE_ALL, usage = pagecache + rss.
> -        */
> -       MEM_CGROUP_STAT_CACHE,     /* # of pages charged as cache */
> -       MEM_CGROUP_STAT_RSS,       /* # of pages charged as anon rss */
> -       MEM_CGROUP_STAT_FILE_MAPPED,  /* # of pages charged as file rss */
> -       MEM_CGROUP_STAT_PGPGIN_COUNT,   /* # of pages paged in */
> -       MEM_CGROUP_STAT_PGPGOUT_COUNT,  /* # of pages paged out */
> -       MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
> -       MEM_CGROUP_STAT_SOFTLIMIT, /* decrements on each page in/out.
> -                                       used by soft limit implementation */
> -       MEM_CGROUP_STAT_THRESHOLDS, /* decrements on each page in/out.
> -                                       used by threshold implementation */
> -
> -       MEM_CGROUP_STAT_NSTATS,
> -};
> -
>  struct mem_cgroup_stat_cpu {
>        s64 count[MEM_CGROUP_STAT_NSTATS];
>  };
>
> +/* Per cgroup page statistics */
> +struct mem_cgroup_page_stat {
> +       enum mem_cgroup_page_stat_item item;
> +       s64 value;
> +};
> +
>  /*
>  * per-zone information in memory controller.
>  */
> @@ -157,6 +142,15 @@ struct mem_cgroup_threshold_ary {
>  static bool mem_cgroup_threshold_check(struct mem_cgroup *mem);
>  static void mem_cgroup_threshold(struct mem_cgroup *mem);
>
> +enum mem_cgroup_dirty_param {
> +       MEM_CGROUP_DIRTY_RATIO,
> +       MEM_CGROUP_DIRTY_BYTES,
> +       MEM_CGROUP_DIRTY_BACKGROUND_RATIO,
> +       MEM_CGROUP_DIRTY_BACKGROUND_BYTES,
> +
> +       MEM_CGROUP_DIRTY_NPARAMS,
> +};
> +
>  /*
>  * The memory controller data structure. The memory controller controls both
>  * page cache and RSS per cgroup. We would eventually like to provide
> @@ -205,6 +199,9 @@ struct mem_cgroup {
>
>        unsigned int    swappiness;
>
> +       /* control memory cgroup dirty pages */
> +       unsigned long dirty_param[MEM_CGROUP_DIRTY_NPARAMS];
> +
>        /* set when res.limit == memsw.limit */
>        bool            memsw_is_minimum;
>
> @@ -1021,6 +1018,164 @@ static unsigned int get_swappiness(struct mem_cgroup *memcg)
>        return swappiness;
>  }
>
> +static unsigned long get_dirty_param(struct mem_cgroup *memcg,
> +                       enum mem_cgroup_dirty_param idx)
> +{
> +       unsigned long ret;
> +
> +       VM_BUG_ON(idx >= MEM_CGROUP_DIRTY_NPARAMS);
> +       spin_lock(&memcg->reclaim_param_lock);
> +       ret = memcg->dirty_param[idx];
> +       spin_unlock(&memcg->reclaim_param_lock);
> +
> +       return ret;
> +}
> +
> +long mem_cgroup_dirty_ratio(void)
> +{
> +       struct mem_cgroup *memcg;
> +       long ret = vm_dirty_ratio;
> +
> +       if (mem_cgroup_disabled())
> +               return ret;
> +       /*
> +        * It's possible that "current" may be moved to other cgroup while we
> +        * access cgroup. But precise check is meaningless because the task can
> +        * be moved after our access and writeback tends to take long time.
> +        * At least, "memcg" will not be freed under rcu_read_lock().
> +        */
> +       rcu_read_lock();
> +       memcg = mem_cgroup_from_task(current);
> +       if (likely(memcg))
> +               ret = get_dirty_param(memcg, MEM_CGROUP_DIRTY_RATIO);
> +       rcu_read_unlock();
> +
> +       return ret;
> +}
> +
> +unsigned long mem_cgroup_dirty_bytes(void)
> +{
> +       struct mem_cgroup *memcg;
> +       unsigned long ret = vm_dirty_bytes;
> +
> +       if (mem_cgroup_disabled())
> +               return ret;
> +       rcu_read_lock();
> +       memcg = mem_cgroup_from_task(current);
> +       if (likely(memcg))
> +               ret = get_dirty_param(memcg, MEM_CGROUP_DIRTY_BYTES);
> +       rcu_read_unlock();
> +
> +       return ret;
> +}
> +
> +long mem_cgroup_dirty_background_ratio(void)
> +{
> +       struct mem_cgroup *memcg;
> +       long ret = dirty_background_ratio;
> +
> +       if (mem_cgroup_disabled())
> +               return ret;
> +       rcu_read_lock();
> +       memcg = mem_cgroup_from_task(current);
> +       if (likely(memcg))
> +               ret = get_dirty_param(memcg, MEM_CGROUP_DIRTY_BACKGROUND_RATIO);
> +       rcu_read_unlock();
> +
> +       return ret;
> +}
> +
> +unsigned long mem_cgroup_dirty_background_bytes(void)
> +{
> +       struct mem_cgroup *memcg;
> +       unsigned long ret = dirty_background_bytes;
> +
> +       if (mem_cgroup_disabled())
> +               return ret;
> +       rcu_read_lock();
> +       memcg = mem_cgroup_from_task(current);
> +       if (likely(memcg))
> +               ret = get_dirty_param(memcg, MEM_CGROUP_DIRTY_BACKGROUND_BYTES);
> +       rcu_read_unlock();
> +
> +       return ret;
> +}
> +
> +static inline bool mem_cgroup_can_swap(struct mem_cgroup *memcg)
> +{
> +       return do_swap_account ?
> +                       res_counter_read_u64(&memcg->memsw, RES_LIMIT) :
> +                       nr_swap_pages > 0;
> +}
> +
> +static s64 mem_cgroup_get_local_page_stat(struct mem_cgroup *memcg,
> +                               enum mem_cgroup_page_stat_item item)
> +{
> +       s64 ret;
> +
> +       switch (item) {
> +       case MEMCG_NR_DIRTYABLE_PAGES:
> +               ret = res_counter_read_u64(&memcg->res, RES_LIMIT) -
> +                       res_counter_read_u64(&memcg->res, RES_USAGE);
> +               /* Translate free memory in pages */
> +               ret >>= PAGE_SHIFT;
> +               ret += mem_cgroup_read_stat(memcg, LRU_ACTIVE_FILE) +
> +                       mem_cgroup_read_stat(memcg, LRU_INACTIVE_FILE);
> +               if (mem_cgroup_can_swap(memcg))
> +                       ret += mem_cgroup_read_stat(memcg, LRU_ACTIVE_ANON) +
> +                               mem_cgroup_read_stat(memcg, LRU_INACTIVE_ANON);
> +               break;
> +       case MEMCG_NR_RECLAIM_PAGES:
> +               ret = mem_cgroup_read_stat(memcg, MEM_CGROUP_STAT_FILE_DIRTY) +
> +                       mem_cgroup_read_stat(memcg,
> +                                       MEM_CGROUP_STAT_UNSTABLE_NFS);
> +               break;
> +       case MEMCG_NR_WRITEBACK:
> +               ret = mem_cgroup_read_stat(memcg, MEM_CGROUP_STAT_WRITEBACK);
> +               break;
> +       case MEMCG_NR_DIRTY_WRITEBACK_PAGES:
> +               ret = mem_cgroup_read_stat(memcg, MEM_CGROUP_STAT_WRITEBACK) +
> +                       mem_cgroup_read_stat(memcg,
> +                               MEM_CGROUP_STAT_UNSTABLE_NFS);
> +               break;
> +       default:
> +               ret = 0;
> +               WARN_ON_ONCE(1);

I think it's a bug, not warning.

> +       }
> +       return ret;
> +}
> +
> +static int mem_cgroup_page_stat_cb(struct mem_cgroup *mem, void *data)
> +{
> +       struct mem_cgroup_page_stat *stat = (struct mem_cgroup_page_stat *)data;
> +
> +       stat->value += mem_cgroup_get_local_page_stat(mem, stat->item);
> +       return 0;
> +}
> +
> +s64 mem_cgroup_page_stat(enum mem_cgroup_page_stat_item item)
> +{
> +       struct mem_cgroup_page_stat stat = {};
> +       struct mem_cgroup *memcg;
> +
> +       if (mem_cgroup_disabled())
> +               return -ENOMEM;

EINVAL/ENOSYS?

> +       rcu_read_lock();
> +       memcg = mem_cgroup_from_task(current);
> +       if (memcg) {
> +               /*
> +                * Recursively evaulate page statistics against all cgroup
> +                * under hierarchy tree
> +                */
> +               stat.item = item;
> +               mem_cgroup_walk_tree(memcg, &stat, mem_cgroup_page_stat_cb);
> +       } else
> +               stat.value = -ENOMEM;

ditto.

> +       rcu_read_unlock();
> +
> +       return stat.value;
> +}
> +
>  static int mem_cgroup_count_children_cb(struct mem_cgroup *mem, void *data)
>  {
>        int *val = data;
> @@ -1263,14 +1418,16 @@ static void record_last_oom(struct mem_cgroup *mem)
>  }
>
>  /*
> - * Currently used to update mapped file statistics, but the routine can be
> - * generalized to update other statistics as well.
> + * Generalized routine to update memory cgroup statistics.
>  */
> -void mem_cgroup_update_file_mapped(struct page *page, int val)
> +void mem_cgroup_update_stat(struct page *page,
> +                       enum mem_cgroup_stat_index idx, int val)

EXPORT_SYMBOL_GPL(mem_cgroup_update_stat) is needed, since
it uses by filesystems.

>  {
>        struct mem_cgroup *mem;
>        struct page_cgroup *pc;
>
> +       if (mem_cgroup_disabled())
> +               return;
>        pc = lookup_page_cgroup(page);
>        if (unlikely(!pc))
>                return;
> @@ -1286,7 +1443,8 @@ void mem_cgroup_update_file_mapped(struct page *page, int val)
>        /*
>         * Preemption is already disabled. We can use __this_cpu_xxx
>         */
> -       __this_cpu_add(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED], val);
> +       VM_BUG_ON(idx >= MEM_CGROUP_STAT_NSTATS);
> +       __this_cpu_add(mem->stat->count[idx], val);
>
>  done:
>        unlock_page_cgroup(pc);
> @@ -3033,6 +3191,10 @@ enum {
>        MCS_PGPGIN,
>        MCS_PGPGOUT,
>        MCS_SWAP,
> +       MCS_FILE_DIRTY,
> +       MCS_WRITEBACK,
> +       MCS_WRITEBACK_TEMP,
> +       MCS_UNSTABLE_NFS,
>        MCS_INACTIVE_ANON,
>        MCS_ACTIVE_ANON,
>        MCS_INACTIVE_FILE,
> @@ -3055,6 +3217,10 @@ struct {
>        {"pgpgin", "total_pgpgin"},
>        {"pgpgout", "total_pgpgout"},
>        {"swap", "total_swap"},
> +       {"filedirty", "dirty_pages"},
> +       {"writeback", "writeback_pages"},
> +       {"writeback_tmp", "writeback_temp_pages"},
> +       {"nfs", "nfs_unstable"},
>        {"inactive_anon", "total_inactive_anon"},
>        {"active_anon", "total_active_anon"},
>        {"inactive_file", "total_inactive_file"},
> @@ -3083,6 +3249,14 @@ static int mem_cgroup_get_local_stat(struct mem_cgroup *mem, void *data)
>                val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_SWAPOUT);
>                s->stat[MCS_SWAP] += val * PAGE_SIZE;
>        }
> +       val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_FILE_DIRTY);
> +       s->stat[MCS_FILE_DIRTY] += val;
> +       val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_WRITEBACK);
> +       s->stat[MCS_WRITEBACK] += val;
> +       val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_WRITEBACK_TEMP);
> +       s->stat[MCS_WRITEBACK_TEMP] += val;
> +       val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_UNSTABLE_NFS);
> +       s->stat[MCS_UNSTABLE_NFS] += val;
>
>        /* per zone stat */
>        val = mem_cgroup_get_local_zonestat(mem, LRU_INACTIVE_ANON);
> @@ -3467,6 +3641,50 @@ unlock:
>        return ret;
>  }
>
> +static u64 mem_cgroup_dirty_read(struct cgroup *cgrp, struct cftype *cft)
> +{
> +       struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
> +       int type = cft->private;
> +
> +       return get_dirty_param(memcg, type);
> +}
> +
> +static int
> +mem_cgroup_dirty_write(struct cgroup *cgrp, struct cftype *cft, u64 val)
> +{
> +       struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
> +       int type = cft->private;
> +
> +       if (cgrp->parent == NULL)
> +               return -EINVAL;
> +       if (((type == MEM_CGROUP_DIRTY_RATIO) ||
> +               (type == MEM_CGROUP_DIRTY_BACKGROUND_RATIO)) && (val > 100))

Too many unnecessary brackets

if ((type == MEM_CGROUP_DIRTY_RATIO ||
type == MEM_CGROUP_DIRTY_BACKGROUND_RATIO) && val > 100)
> +               return -EINVAL;
> +
> +       spin_lock(&memcg->reclaim_param_lock);
> +       switch (type) {
> +       case MEM_CGROUP_DIRTY_RATIO:
> +               memcg->dirty_param[MEM_CGROUP_DIRTY_RATIO] = val;
> +               memcg->dirty_param[MEM_CGROUP_DIRTY_BYTES] = 0;
> +               break;
> +       case MEM_CGROUP_DIRTY_BYTES:
> +               memcg->dirty_param[MEM_CGROUP_DIRTY_RATIO] = 0;
> +               memcg->dirty_param[MEM_CGROUP_DIRTY_BYTES] = val;
> +               break;
> +       case MEM_CGROUP_DIRTY_BACKGROUND_RATIO:
> +               memcg->dirty_param[MEM_CGROUP_DIRTY_BACKGROUND_RATIO] = val;
> +               memcg->dirty_param[MEM_CGROUP_DIRTY_BACKGROUND_BYTES] = 0;
> +               break;
> +       case MEM_CGROUP_DIRTY_BACKGROUND_BYTES:
> +               memcg->dirty_param[MEM_CGROUP_DIRTY_BACKGROUND_RATIO] = 0;
> +               memcg->dirty_param[MEM_CGROUP_DIRTY_BACKGROUND_BYTES] = val;
> +               break;
> +       }
> +       spin_unlock(&memcg->reclaim_param_lock);
> +
> +       return 0;
> +}
> +
>  static struct cftype mem_cgroup_files[] = {
>        {
>                .name = "usage_in_bytes",
> @@ -3518,6 +3736,30 @@ static struct cftype mem_cgroup_files[] = {
>                .write_u64 = mem_cgroup_swappiness_write,
>        },
>        {
> +               .name = "dirty_ratio",
> +               .read_u64 = mem_cgroup_dirty_read,
> +               .write_u64 = mem_cgroup_dirty_write,
> +               .private = MEM_CGROUP_DIRTY_RATIO,
> +       },
> +       {
> +               .name = "dirty_bytes",
> +               .read_u64 = mem_cgroup_dirty_read,
> +               .write_u64 = mem_cgroup_dirty_write,
> +               .private = MEM_CGROUP_DIRTY_BYTES,
> +       },
> +       {
> +               .name = "dirty_background_ratio",
> +               .read_u64 = mem_cgroup_dirty_read,
> +               .write_u64 = mem_cgroup_dirty_write,
> +               .private = MEM_CGROUP_DIRTY_BACKGROUND_RATIO,
> +       },
> +       {
> +               .name = "dirty_background_bytes",
> +               .read_u64 = mem_cgroup_dirty_read,
> +               .write_u64 = mem_cgroup_dirty_write,
> +               .private = MEM_CGROUP_DIRTY_BACKGROUND_BYTES,
> +       },
> +       {
>                .name = "move_charge_at_immigrate",
>                .read_u64 = mem_cgroup_move_charge_read,
>                .write_u64 = mem_cgroup_move_charge_write,
> @@ -3725,6 +3967,19 @@ static int mem_cgroup_soft_limit_tree_init(void)
>        return 0;
>  }
>
> +/*
> + * NOTE: called only with &src->reclaim_param_lock held from
> + * mem_cgroup_create().
> + */
> +static inline void
> +copy_dirty_params(struct mem_cgroup *dst, struct mem_cgroup *src)
> +{
> +       int i;
> +
> +       for (i = 0; i < MEM_CGROUP_DIRTY_NPARAMS; i++)
> +               dst->dirty_param[i] = src->dirty_param[i];
> +}
> +
>  static struct cgroup_subsys_state * __ref
>  mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
>  {
> @@ -3776,8 +4031,37 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
>        mem->last_scanned_child = 0;
>        spin_lock_init(&mem->reclaim_param_lock);
>
> -       if (parent)
> +       if (parent) {
>                mem->swappiness = get_swappiness(parent);
> +
> +               spin_lock(&parent->reclaim_param_lock);
> +               copy_dirty_params(mem, parent);
> +               spin_unlock(&parent->reclaim_param_lock);
> +       } else {
> +               /*
> +                * XXX: should we need a lock here? we could switch from
> +                * vm_dirty_ratio to vm_dirty_bytes or vice versa but we're not
> +                * reading them atomically. The same for dirty_background_ratio
> +                * and dirty_background_bytes.
> +                *
> +                * For now, try to read them speculatively and retry if a
> +                * "conflict" is detected.
> +                */
> +               do {
> +                       mem->dirty_param[MEM_CGROUP_DIRTY_RATIO] =
> +                                               vm_dirty_ratio;
> +                       mem->dirty_param[MEM_CGROUP_DIRTY_BYTES] =
> +                                               vm_dirty_bytes;
> +               } while (mem->dirty_param[MEM_CGROUP_DIRTY_RATIO] &&
> +                        mem->dirty_param[MEM_CGROUP_DIRTY_BYTES]);
> +               do {
> +                       mem->dirty_param[MEM_CGROUP_DIRTY_BACKGROUND_RATIO] =
> +                                               dirty_background_ratio;
> +                       mem->dirty_param[MEM_CGROUP_DIRTY_BACKGROUND_BYTES] =
> +                                               dirty_background_bytes;
> +               } while (mem->dirty_param[MEM_CGROUP_DIRTY_BACKGROUND_RATIO] &&
> +                       mem->dirty_param[MEM_CGROUP_DIRTY_BACKGROUND_BYTES]);
> +       }
>        atomic_set(&mem->refcnt, 1);
>        mem->move_charge_at_immigrate = 0;
>        mutex_init(&mem->thresholds_lock);
> --
> 1.6.3.3
>
>
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