diff options
| -rw-r--r-- | Documentation/cgroups/memory.txt | 56 | ||||
| -rw-r--r-- | mm/memcontrol.c | 97 |
2 files changed, 147 insertions, 6 deletions
diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt index b871f2552b45..e726fb0df719 100644 --- a/Documentation/cgroups/memory.txt +++ b/Documentation/cgroups/memory.txt @@ -262,10 +262,12 @@ some of the pages cached in the cgroup (page cache pages). 4.2 Task migration When a task migrates from one cgroup to another, it's charge is not -carried forward. The pages allocated from the original cgroup still +carried forward by default. The pages allocated from the original cgroup still remain charged to it, the charge is dropped when the page is freed or reclaimed. +Note: You can move charges of a task along with task migration. See 8. + 4.3 Removing a cgroup A cgroup can be removed by rmdir, but as discussed in sections 4.1 and 4.2, a @@ -414,7 +416,57 @@ NOTE1: Soft limits take effect over a long period of time, since they involve NOTE2: It is recommended to set the soft limit always below the hard limit, otherwise the hard limit will take precedence. -8. TODO +8. Move charges at task migration + +Users can move charges associated with a task along with task migration, that +is, uncharge task's pages from the old cgroup and charge them to the new cgroup. + +8.1 Interface + +This feature is disabled by default. It can be enabled(and disabled again) by +writing to memory.move_charge_at_immigrate of the destination cgroup. + +If you want to enable it: + +# echo (some positive value) > memory.move_charge_at_immigrate + +Note: Each bits of move_charge_at_immigrate has its own meaning about what type + of charges should be moved. See 8.2 for details. +Note: Charges are moved only when you move mm->owner, IOW, a leader of a thread + group. +Note: If we cannot find enough space for the task in the destination cgroup, we + try to make space by reclaiming memory. Task migration may fail if we + cannot make enough space. +Note: It can take several seconds if you move charges in giga bytes order. + +And if you want disable it again: + +# echo 0 > memory.move_charge_at_immigrate + +8.2 Type of charges which can be move + +Each bits of move_charge_at_immigrate has its own meaning about what type of +charges should be moved. + + bit | what type of charges would be moved ? + -----+------------------------------------------------------------------------ + 0 | A charge of an anonymous page(or swap of it) used by the target task. + | Those pages and swaps must be used only by the target task. You must + | enable Swap Extension(see 2.4) to enable move of swap charges. + +Note: Those pages and swaps must be charged to the old cgroup. +Note: More type of pages(e.g. file cache, shmem,) will be supported by other + bits in future. + +8.3 TODO + +- Add support for other types of pages(e.g. file cache, shmem, etc.). +- Implement madvise(2) to let users decide the vma to be moved or not to be + moved. +- All of moving charge operations are done under cgroup_mutex. It's not good + behavior to hold the mutex too long, so we may need some trick. + +9. TODO 1. Add support for accounting huge pages (as a separate controller) 2. Make per-cgroup scanner reclaim not-shared pages first diff --git a/mm/memcontrol.c b/mm/memcontrol.c index d813823ab08f..59ffaf511d77 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -226,11 +226,26 @@ struct mem_cgroup { bool memsw_is_minimum; /* + * Should we move charges of a task when a task is moved into this + * mem_cgroup ? And what type of charges should we move ? + */ + unsigned long move_charge_at_immigrate; + + /* * statistics. This must be placed at the end of memcg. */ struct mem_cgroup_stat stat; }; +/* Stuffs for move charges at task migration. */ +/* + * Types of charges to be moved. "move_charge_at_immitgrate" is treated as a + * left-shifted bitmap of these types. + */ +enum move_type { + NR_MOVE_TYPE, +}; + /* * Maximum loops in mem_cgroup_hierarchical_reclaim(), used for soft * limit reclaim to prevent infinite loops, if they ever occur. @@ -2865,6 +2880,31 @@ static int mem_cgroup_reset(struct cgroup *cont, unsigned int event) return 0; } +static u64 mem_cgroup_move_charge_read(struct cgroup *cgrp, + struct cftype *cft) +{ + return mem_cgroup_from_cont(cgrp)->move_charge_at_immigrate; +} + +static int mem_cgroup_move_charge_write(struct cgroup *cgrp, + struct cftype *cft, u64 val) +{ + struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp); + + if (val >= (1 << NR_MOVE_TYPE)) + return -EINVAL; + /* + * We check this value several times in both in can_attach() and + * attach(), so we need cgroup lock to prevent this value from being + * inconsistent. + */ + cgroup_lock(); + mem->move_charge_at_immigrate = val; + cgroup_unlock(); + + return 0; +} + /* For read statistics */ enum { @@ -3098,6 +3138,11 @@ static struct cftype mem_cgroup_files[] = { .read_u64 = mem_cgroup_swappiness_read, .write_u64 = mem_cgroup_swappiness_write, }, + { + .name = "move_charge_at_immigrate", + .read_u64 = mem_cgroup_move_charge_read, + .write_u64 = mem_cgroup_move_charge_write, + }, }; #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP @@ -3345,6 +3390,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont) if (parent) mem->swappiness = get_swappiness(parent); atomic_set(&mem->refcnt, 1); + mem->move_charge_at_immigrate = 0; return &mem->css; free_out: __mem_cgroup_free(mem); @@ -3381,16 +3427,57 @@ static int mem_cgroup_populate(struct cgroup_subsys *ss, return ret; } +/* Handlers for move charge at task migration. */ +static int mem_cgroup_can_move_charge(void) +{ + return 0; +} + +static int mem_cgroup_can_attach(struct cgroup_subsys *ss, + struct cgroup *cgroup, + struct task_struct *p, + bool threadgroup) +{ + int ret = 0; + struct mem_cgroup *mem = mem_cgroup_from_cont(cgroup); + + if (mem->move_charge_at_immigrate) { + struct mm_struct *mm; + struct mem_cgroup *from = mem_cgroup_from_task(p); + + VM_BUG_ON(from == mem); + + mm = get_task_mm(p); + if (!mm) + return 0; + + /* We move charges only when we move a owner of the mm */ + if (mm->owner == p) + ret = mem_cgroup_can_move_charge(); + + mmput(mm); + } + return ret; +} + +static void mem_cgroup_cancel_attach(struct cgroup_subsys *ss, + struct cgroup *cgroup, + struct task_struct *p, + bool threadgroup) +{ +} + +static void mem_cgroup_move_charge(void) +{ +} + static void mem_cgroup_move_task(struct cgroup_subsys *ss, struct cgroup *cont, struct cgroup *old_cont, struct task_struct *p, bool threadgroup) { - /* - * FIXME: It's better to move charges of this process from old - * memcg to new memcg. But it's just on TODO-List now. - */ + mem_cgroup_move_charge(); } struct cgroup_subsys mem_cgroup_subsys = { @@ -3400,6 +3487,8 @@ struct cgroup_subsys mem_cgroup_subsys = { .pre_destroy = mem_cgroup_pre_destroy, .destroy = mem_cgroup_destroy, .populate = mem_cgroup_populate, + .can_attach = mem_cgroup_can_attach, + .cancel_attach = mem_cgroup_cancel_attach, .attach = mem_cgroup_move_task, .early_init = 0, .use_id = 1, |