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: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: KAMEZAWA 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 59ffaf5..22f088f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -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 @@
* 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 @@
* 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 @@
/*
* 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 @@
}
/* 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 @@
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 @@
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 @@
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 = {