Commit 4ffef5fe authored by Daisuke Nishimura's avatar Daisuke Nishimura Committed by Linus Torvalds

memcg: move charges of anonymous page

This patch is the core part of this move-charge-at-task-migration feature.
 It implements functions to move charges of anonymous pages mapped only by
the target task.

Implementation:
- define struct move_charge_struct and a valuable of it(mc) to remember the
  count of pre-charges and other information.
- At can_attach(), get anon_rss of the target mm, call __mem_cgroup_try_charge()
  repeatedly and count up mc.precharge.
- At attach(), parse the page table, find a target page to be move, and call
  mem_cgroup_move_account() about the page.
- Cancel all precharges if mc.precharge > 0 on failure or at the end of
  task move.

[akpm@linux-foundation.org: a little simplification]
Signed-off-by: default avatarDaisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7dc74be0
......@@ -21,6 +21,7 @@
#include <linux/memcontrol.h>
#include <linux/cgroup.h>
#include <linux/mm.h>
#include <linux/hugetlb.h>
#include <linux/pagemap.h>
#include <linux/smp.h>
#include <linux/page-flags.h>
......@@ -243,9 +244,17 @@ struct mem_cgroup {
* left-shifted bitmap of these types.
*/
enum move_type {
MOVE_CHARGE_TYPE_ANON, /* private anonymous page and swap of it */
NR_MOVE_TYPE,
};
/* "mc" and its members are protected by cgroup_mutex */
static struct move_charge_struct {
struct mem_cgroup *from;
struct mem_cgroup *to;
unsigned long precharge;
} mc;
/*
* Maximum loops in mem_cgroup_hierarchical_reclaim(), used for soft
* limit reclaim to prevent infinite loops, if they ever occur.
......@@ -1513,7 +1522,7 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
* Insert ancestor (and ancestor's ancestors), to softlimit RB-tree.
* if they exceeds softlimit.
*/
if (mem_cgroup_soft_limit_check(mem))
if (page && mem_cgroup_soft_limit_check(mem))
mem_cgroup_update_tree(mem, page);
done:
return 0;
......@@ -1690,8 +1699,9 @@ static void __mem_cgroup_move_account(struct page_cgroup *pc,
/*
* We charges against "to" which may not have any tasks. Then, "to"
* can be under rmdir(). But in current implementation, caller of
* this function is just force_empty() and it's garanteed that
* "to" is never removed. So, we don't check rmdir status here.
* this function is just force_empty() and move charge, so it's
* garanteed that "to" is never removed. So, we don't check rmdir
* status here.
*/
}
......@@ -3428,11 +3438,171 @@ static int mem_cgroup_populate(struct cgroup_subsys *ss,
}
/* Handlers for move charge at task migration. */
static int mem_cgroup_can_move_charge(void)
static int mem_cgroup_do_precharge(void)
{
int ret = -ENOMEM;
struct mem_cgroup *mem = mc.to;
ret = __mem_cgroup_try_charge(NULL, GFP_KERNEL, &mem, false, NULL);
if (ret || !mem)
return -ENOMEM;
mc.precharge++;
return ret;
}
/**
* is_target_pte_for_mc - check a pte whether it is valid for move charge
* @vma: the vma the pte to be checked belongs
* @addr: the address corresponding to the pte to be checked
* @ptent: the pte to be checked
* @target: the pointer the target page will be stored(can be NULL)
*
* Returns
* 0(MC_TARGET_NONE): if the pte is not a target for move charge.
* 1(MC_TARGET_PAGE): if the page corresponding to this pte is a target for
* move charge. if @target is not NULL, the page is stored in target->page
* with extra refcnt got(Callers should handle it).
*
* Called with pte lock held.
*/
/* We add a new member later. */
union mc_target {
struct page *page;
};
/* We add a new type later. */
enum mc_target_type {
MC_TARGET_NONE, /* not used */
MC_TARGET_PAGE,
};
static int is_target_pte_for_mc(struct vm_area_struct *vma,
unsigned long addr, pte_t ptent, union mc_target *target)
{
struct page *page;
struct page_cgroup *pc;
int ret = 0;
bool move_anon = test_bit(MOVE_CHARGE_TYPE_ANON,
&mc.to->move_charge_at_immigrate);
if (!pte_present(ptent))
return 0;
page = vm_normal_page(vma, addr, ptent);
if (!page || !page_mapped(page))
return 0;
/*
* TODO: We don't move charges of file(including shmem/tmpfs) pages for
* now.
*/
if (!move_anon || !PageAnon(page))
return 0;
/*
* TODO: We don't move charges of shared(used by multiple processes)
* pages for now.
*/
if (page_mapcount(page) > 1)
return 0;
if (!get_page_unless_zero(page))
return 0;
pc = lookup_page_cgroup(page);
/*
* Do only loose check w/o page_cgroup lock. mem_cgroup_move_account()
* checks the pc is valid or not under the lock.
*/
if (PageCgroupUsed(pc) && pc->mem_cgroup == mc.from) {
ret = MC_TARGET_PAGE;
if (target)
target->page = page;
}
if (!ret || !target)
put_page(page);
return ret;
}
static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd,
unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
struct vm_area_struct *vma = walk->private;
pte_t *pte;
spinlock_t *ptl;
pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
for (; addr != end; pte++, addr += PAGE_SIZE)
if (is_target_pte_for_mc(vma, addr, *pte, NULL))
mc.precharge++; /* increment precharge temporarily */
pte_unmap_unlock(pte - 1, ptl);
cond_resched();
return 0;
}
static unsigned long mem_cgroup_count_precharge(struct mm_struct *mm)
{
unsigned long precharge;
struct vm_area_struct *vma;
down_read(&mm->mmap_sem);
for (vma = mm->mmap; vma; vma = vma->vm_next) {
struct mm_walk mem_cgroup_count_precharge_walk = {
.pmd_entry = mem_cgroup_count_precharge_pte_range,
.mm = mm,
.private = vma,
};
if (is_vm_hugetlb_page(vma))
continue;
/* TODO: We don't move charges of shmem/tmpfs pages for now. */
if (vma->vm_flags & VM_SHARED)
continue;
walk_page_range(vma->vm_start, vma->vm_end,
&mem_cgroup_count_precharge_walk);
}
up_read(&mm->mmap_sem);
precharge = mc.precharge;
mc.precharge = 0;
return precharge;
}
#define PRECHARGE_AT_ONCE 256
static int mem_cgroup_precharge_mc(struct mm_struct *mm)
{
int ret = 0;
int count = PRECHARGE_AT_ONCE;
unsigned long precharge = mem_cgroup_count_precharge(mm);
while (!ret && precharge--) {
if (signal_pending(current)) {
ret = -EINTR;
break;
}
if (!count--) {
count = PRECHARGE_AT_ONCE;
cond_resched();
}
ret = mem_cgroup_do_precharge();
}
return ret;
}
static void mem_cgroup_clear_mc(void)
{
/* we must uncharge all the leftover precharges from mc.to */
while (mc.precharge) {
mem_cgroup_cancel_charge(mc.to);
mc.precharge--;
}
mc.from = NULL;
mc.to = NULL;
}
static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
struct cgroup *cgroup,
struct task_struct *p,
......@@ -3450,11 +3620,19 @@ static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
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();
if (mm->owner == p) {
VM_BUG_ON(mc.from);
VM_BUG_ON(mc.to);
VM_BUG_ON(mc.precharge);
mc.from = from;
mc.to = mem;
mc.precharge = 0;
ret = mem_cgroup_precharge_mc(mm);
if (ret)
mem_cgroup_clear_mc();
}
mmput(mm);
}
return ret;
......@@ -3465,10 +3643,95 @@ static void mem_cgroup_cancel_attach(struct cgroup_subsys *ss,
struct task_struct *p,
bool threadgroup)
{
mem_cgroup_clear_mc();
}
static void mem_cgroup_move_charge(void)
static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
int ret = 0;
struct vm_area_struct *vma = walk->private;
pte_t *pte;
spinlock_t *ptl;
retry:
pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
for (; addr != end; addr += PAGE_SIZE) {
pte_t ptent = *(pte++);
union mc_target target;
int type;
struct page *page;
struct page_cgroup *pc;
if (!mc.precharge)
break;
type = is_target_pte_for_mc(vma, addr, ptent, &target);
switch (type) {
case MC_TARGET_PAGE:
page = target.page;
if (isolate_lru_page(page))
goto put;
pc = lookup_page_cgroup(page);
if (!mem_cgroup_move_account(pc, mc.from, mc.to)) {
css_put(&mc.to->css);
mc.precharge--;
}
putback_lru_page(page);
put: /* is_target_pte_for_mc() gets the page */
put_page(page);
break;
default:
break;
}
}
pte_unmap_unlock(pte - 1, ptl);
cond_resched();
if (addr != end) {
/*
* We have consumed all precharges we got in can_attach().
* We try charge one by one, but don't do any additional
* charges to mc.to if we have failed in charge once in attach()
* phase.
*/
ret = mem_cgroup_do_precharge();
if (!ret)
goto retry;
}
return ret;
}
static void mem_cgroup_move_charge(struct mm_struct *mm)
{
struct vm_area_struct *vma;
lru_add_drain_all();
down_read(&mm->mmap_sem);
for (vma = mm->mmap; vma; vma = vma->vm_next) {
int ret;
struct mm_walk mem_cgroup_move_charge_walk = {
.pmd_entry = mem_cgroup_move_charge_pte_range,
.mm = mm,
.private = vma,
};
if (is_vm_hugetlb_page(vma))
continue;
/* TODO: We don't move charges of shmem/tmpfs pages for now. */
if (vma->vm_flags & VM_SHARED)
continue;
ret = walk_page_range(vma->vm_start, vma->vm_end,
&mem_cgroup_move_charge_walk);
if (ret)
/*
* means we have consumed all precharges and failed in
* doing additional charge. Just abandon here.
*/
break;
}
up_read(&mm->mmap_sem);
}
static void mem_cgroup_move_task(struct cgroup_subsys *ss,
......@@ -3477,7 +3740,18 @@ static void mem_cgroup_move_task(struct cgroup_subsys *ss,
struct task_struct *p,
bool threadgroup)
{
mem_cgroup_move_charge();
struct mm_struct *mm;
if (!mc.to)
/* no need to move charge */
return;
mm = get_task_mm(p);
if (mm) {
mem_cgroup_move_charge(mm);
mmput(mm);
}
mem_cgroup_clear_mc();
}
struct cgroup_subsys mem_cgroup_subsys = {
......
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