memcg: move charges of anonymous swap
This patch is another core part of this move-charge-at-task-migration
feature. It enables moving charges of anonymous swaps.
To move the charge of swap, we need to exchange swap_cgroup's record.
In current implementation, swap_cgroup's record is protected by:
- page lock: if the entry is on swap cache.
- swap_lock: if the entry is not on swap cache.
This works well in usual swap-in/out activity.
But this behavior make the feature of moving swap charge check many
conditions to exchange swap_cgroup's record safely.
So I changed modification of swap_cgroup's recored(swap_cgroup_record())
to use xchg, and define a new function to cmpxchg swap_cgroup's record.
This patch also enables moving charge of non pte_present but not uncharged
swap caches, which can be exist on swap-out path, by getting the target
pages via find_get_page() as do_mincore() does.
[kosaki.motohiro@jp.fujitsu.com: fix ia64 build]
[akpm@linux-foundation.org: fix typos]
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: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
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 589084f..e883198 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -33,6 +33,7 @@
#include <linux/rbtree.h>
#include <linux/slab.h>
#include <linux/swap.h>
+#include <linux/swapops.h>
#include <linux/spinlock.h>
#include <linux/fs.h>
#include <linux/seq_file.h>
@@ -2270,6 +2271,54 @@
}
rcu_read_unlock();
}
+
+/**
+ * mem_cgroup_move_swap_account - move swap charge and swap_cgroup's record.
+ * @entry: swap entry to be moved
+ * @from: mem_cgroup which the entry is moved from
+ * @to: mem_cgroup which the entry is moved to
+ *
+ * It succeeds only when the swap_cgroup's record for this entry is the same
+ * as the mem_cgroup's id of @from.
+ *
+ * Returns 0 on success, -EINVAL on failure.
+ *
+ * The caller must have charged to @to, IOW, called res_counter_charge() about
+ * both res and memsw, and called css_get().
+ */
+static int mem_cgroup_move_swap_account(swp_entry_t entry,
+ struct mem_cgroup *from, struct mem_cgroup *to)
+{
+ unsigned short old_id, new_id;
+
+ old_id = css_id(&from->css);
+ new_id = css_id(&to->css);
+
+ if (swap_cgroup_cmpxchg(entry, old_id, new_id) == old_id) {
+ if (!mem_cgroup_is_root(from))
+ res_counter_uncharge(&from->memsw, PAGE_SIZE);
+ mem_cgroup_swap_statistics(from, false);
+ mem_cgroup_put(from);
+ /*
+ * we charged both to->res and to->memsw, so we should uncharge
+ * to->res.
+ */
+ if (!mem_cgroup_is_root(to))
+ res_counter_uncharge(&to->res, PAGE_SIZE);
+ mem_cgroup_swap_statistics(to, true);
+ mem_cgroup_get(to);
+ css_put(&to->css);
+
+ return 0;
+ }
+ return -EINVAL;
+}
+#else
+static inline int mem_cgroup_move_swap_account(swp_entry_t entry,
+ struct mem_cgroup *from, struct mem_cgroup *to)
+{
+ return -EINVAL;
+}
#endif
/*
@@ -2949,6 +2998,7 @@
return mem_cgroup_from_cont(cgrp)->move_charge_at_immigrate;
}
+#ifdef CONFIG_MMU
static int mem_cgroup_move_charge_write(struct cgroup *cgrp,
struct cftype *cft, u64 val)
{
@@ -2967,6 +3017,13 @@
return 0;
}
+#else
+static int mem_cgroup_move_charge_write(struct cgroup *cgrp,
+ struct cftype *cft, u64 val)
+{
+ return -ENOSYS;
+}
+#endif
/* For read statistics */
@@ -3489,6 +3546,7 @@
return ret;
}
+#ifdef CONFIG_MMU
/* Handlers for move charge at task migration. */
#define PRECHARGE_COUNT_AT_ONCE 256
static int mem_cgroup_do_precharge(unsigned long count)
@@ -3544,77 +3602,124 @@
}
return ret;
}
+#else /* !CONFIG_MMU */
+static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
+ struct cgroup *cgroup,
+ struct task_struct *p,
+ bool threadgroup)
+{
+ return 0;
+}
+static void mem_cgroup_cancel_attach(struct cgroup_subsys *ss,
+ struct cgroup *cgroup,
+ struct task_struct *p,
+ bool threadgroup)
+{
+}
+static void mem_cgroup_move_task(struct cgroup_subsys *ss,
+ struct cgroup *cont,
+ struct cgroup *old_cont,
+ struct task_struct *p,
+ bool threadgroup)
+{
+}
+#endif
/**
* 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)
+ * @target: the pointer the target page or swap ent 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).
+ * 2(MC_TARGET_SWAP): if the swap entry corresponding to this pte is a
+ * target for charge migration. if @target is not NULL, the entry is stored
+ * in target->ent.
*
* Called with pte lock held.
*/
-/* We add a new member later. */
union mc_target {
struct page *page;
+ swp_entry_t ent;
};
-/* We add a new type later. */
enum mc_target_type {
MC_TARGET_NONE, /* not used */
MC_TARGET_PAGE,
+ MC_TARGET_SWAP,
};
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 *page = NULL;
struct page_cgroup *pc;
int ret = 0;
+ swp_entry_t ent = { .val = 0 };
+ int usage_count = 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 (!pte_present(ptent)) {
+ /* TODO: handle swap of shmes/tmpfs */
+ if (pte_none(ptent) || pte_file(ptent))
+ return 0;
+ else if (is_swap_pte(ptent)) {
+ ent = pte_to_swp_entry(ptent);
+ if (!move_anon || non_swap_entry(ent))
+ return 0;
+ usage_count = mem_cgroup_count_swap_user(ent, &page);
+ }
+ } else {
+ 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;
+ if (!get_page_unless_zero(page))
+ return 0;
+ usage_count = page_mapcount(page);
}
-
- if (!ret || !target)
- put_page(page);
-
+ if (usage_count > 1) {
+ /*
+ * TODO: We don't move charges of shared(used by multiple
+ * processes) pages for now.
+ */
+ if (page)
+ put_page(page);
+ return 0;
+ }
+ if (page) {
+ 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);
+ }
+ /* throught */
+ if (ent.val && do_swap_account && !ret &&
+ css_id(&mc.from->css) == lookup_swap_cgroup(ent)) {
+ ret = MC_TARGET_SWAP;
+ if (target)
+ target->ent = ent;
+ }
return ret;
}
@@ -3754,6 +3859,7 @@
int type;
struct page *page;
struct page_cgroup *pc;
+ swp_entry_t ent;
if (!mc.precharge)
break;
@@ -3775,6 +3881,11 @@
put: /* is_target_pte_for_mc() gets the page */
put_page(page);
break;
+ case MC_TARGET_SWAP:
+ ent = target.ent;
+ if (!mem_cgroup_move_swap_account(ent, mc.from, mc.to))
+ mc.precharge--;
+ break;
default:
break;
}