KAMEZAWA Hiroyuki wrote:
> This patch adds an interface "memory.force_empty".
> Any write to this file will drop all charges in this cgroup if
> there is no task under.
>
> %echo 1 > /....../memory.force_empty
>
> will drop all charges of memory cgroup if cgroup's tasks is empty.
>
> This is useful to invoke rmdir() against memory cgroup successfully.
>
> Tested and worked well on x86_64/fake-NUMA system.
>
> Changelog v4 -> v5:
> - added comments to mem_cgroup_force_empty()
> - made mem_force_empty_read return -EINVAL
> - cleanup mem_cgroup_force_empty_list()
> - removed SWAP_CLUSTER_MAX
>
> Changelog v3 -> v4:
> - adjusted to 2.6.23-mm1
> - fixed typo
> - changes buf[2]="0" to static const
>
> Changelog v2 -> v3:
> - changed the name from force_reclaim to force_empty.
>
> Changelog v1 -> v2:
> - added a new interface force_reclaim.
> - changes spin_lock to spin_lock_irqsave().
>
>
> Signed-off-by: KAMEZAWA Hiroyuki <[EMAIL PROTECTED]>
>
>
> mm/memcontrol.c | 110
> ++++++++++++++++++++++++++++++++++++++++++++++++++++----
> 1 file changed, 103 insertions(+), 7 deletions(-)
>
> Index: devel-2.6.23-mm1/mm/memcontrol.c
> ===================================================================
> --- devel-2.6.23-mm1.orig/mm/memcontrol.c
> +++ devel-2.6.23-mm1/mm/memcontrol.c
> @@ -480,6 +480,7 @@ void mem_cgroup_uncharge(struct page_cgr
> page = pc->page;
> /*
> * get page->cgroup and clear it under lock.
> + * force_empty can drop page->cgroup without checking refcnt.
> */
> if (clear_page_cgroup(page, pc) == pc) {
> mem = pc->mem_cgroup;
> @@ -489,13 +490,6 @@ void mem_cgroup_uncharge(struct page_cgr
> list_del_init(&pc->lru);
> spin_unlock_irqrestore(&mem->lru_lock, flags);
> kfree(pc);
> - } else {
> - /*
> - * Note:This will be removed when force-empty patch is
> - * applied. just show warning here.
> - */
> - printk(KERN_ERR "Race in mem_cgroup_uncharge() ?");
> - dump_stack();
> }
> }
> }
> @@ -543,6 +537,76 @@ retry:
> return;
> }
>
> +/*
> + * This routine traverse page_cgroup in given list and drop them all.
> + * This routine ignores page_cgroup->ref_cnt.
> + * *And* this routine doesn't reclaim page itself, just removes page_cgroup.
> + */
> +#define FORCE_UNCHARGE_BATCH (128)
> +static void
> +mem_cgroup_force_empty_list(struct mem_cgroup *mem, struct list_head *list)
> +{
> + struct page_cgroup *pc;
> + struct page *page;
> + int count;
> + unsigned long flags;
> +
> +retry:
> + count = FORCE_UNCHARGE_BATCH;
> + spin_lock_irqsave(&mem->lru_lock, flags);
> +
> + while (--count && !list_empty(list)) {
> + pc = list_entry(list->prev, struct page_cgroup, lru);
> + page = pc->page;
> + /* Avoid race with charge */
> + atomic_set(&pc->ref_cnt, 0);
> + if (clear_page_cgroup(page, pc) == pc) {
> + css_put(&mem->css);
> + res_counter_uncharge(&mem->res, PAGE_SIZE);
> + list_del_init(&pc->lru);
> + kfree(pc);
> + } else /* being uncharged ? ...do relax */
> + break;
> + }
> + spin_unlock_irqrestore(&mem->lru_lock, flags);
> + if (!list_empty(list)) {
> + cond_resched();
> + goto retry;
> + }
> + return;
> +}
> +
We could potentially share some of this code with the background reclaim
code being worked upon by YAMAMOTO-San.
> +/*
> + * make mem_cgroup's charge to be 0 if there is no task.
> + * This enables deleting this mem_cgroup.
> + */
> +
> +int mem_cgroup_force_empty(struct mem_cgroup *mem)
> +{
> + int ret = -EBUSY;
> + css_get(&mem->css);
> + /*
> + * page reclaim code (kswapd etc..) will move pages between
> +` * active_list <-> inactive_list while we don't take a lock.
> + * So, we have to do loop here until all lists are empty.
> + */
> + while (!(list_empty(&mem->active_list) &&
> + list_empty(&mem->inactive_list))) {
> + if (atomic_read(&mem->css.cgroup->count) > 0)
> + goto out;
> + /* drop all page_cgroup in active_list */
> + mem_cgroup_force_empty_list(mem, &mem->active_list);
> + /* drop all page_cgroup in inactive_list */
> + mem_cgroup_force_empty_list(mem, &mem->inactive_list);
> + }
> + ret = 0;
> +out:
> + css_put(&mem->css);
> + return ret;
> +}
> +
> +
> +
> int mem_cgroup_write_strategy(char *buf, unsigned long long *tmp)
> {
> *tmp = memparse(buf, &buf);
> @@ -628,6 +692,33 @@ static ssize_t mem_control_type_read(str
> ppos, buf, s - buf);
> }
>
> +
> +static ssize_t mem_force_empty_write(struct cgroup *cont,
> + struct cftype *cft, struct file *file,
> + const char __user *userbuf,
> + size_t nbytes, loff_t *ppos)
> +{
> + struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
> + int ret;
> + ret = mem_cgroup_force_empty(mem);
> + if (!ret)
> + ret = nbytes;
> + return ret;
> +}
> +
> +/*
> + * Note: This should be removed if cgroup supports write-only file.
> + */
> +
> +static ssize_t mem_force_empty_read(struct cgroup *cont,
> + struct cftype *cft,
> + struct file *file, char __user *userbuf,
> + size_t nbytes, loff_t *ppos)
> +{
> + return -EINVAL;
> +}
> +
> +
> static struct cftype mem_cgroup_files[] = {
> {
> .name = "usage_in_bytes",
> @@ -650,6 +741,11 @@ static struct cftype mem_cgroup_files[]
> .write = mem_control_type_write,
> .read = mem_control_type_read,
> },
> + {
> + .name = "force_empty",
> + .write = mem_force_empty_write,
> + .read = mem_force_empty_read,
> + },
> };
>
> static struct mem_cgroup init_mem_cgroup;
>
--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
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