From: Huang Ying <ying.hu...@intel.com>
The swap cgroup uses a kind of discontinuous array to record the
information for the swap entries. lookup_swap_cgroup() provides a good
encapsulation to access one element of the discontinuous array. To make
it easier to access multiple elements of the discontinuous array, an
iterator for the swap cgroup named swap_cgroup_iter is added in this
patch.
This will be used for transparent huge page (THP) swap support. Where
the swap_cgroup for multiple swap entries will be changed together.
Cc: Andrea Arcangeli <aarca...@redhat.com>
Cc: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
Cc: Vladimir Davydov <vdavy...@virtuozzo.com>
Cc: Johannes Weiner <han...@cmpxchg.org>
Cc: Michal Hocko <mho...@kernel.org>
Cc: Tejun Heo <t...@kernel.org>
Cc: cgro...@vger.kernel.org
Signed-off-by: "Huang, Ying" <ying.hu...@intel.com>
---
mm/swap_cgroup.c | 62 +++++++++++++++++++++++++++++++++++++++++---------------
1 file changed, 46 insertions(+), 16 deletions(-)
diff --git a/mm/swap_cgroup.c b/mm/swap_cgroup.c
index 310ac0b..3563b8b 100644
--- a/mm/swap_cgroup.c
+++ b/mm/swap_cgroup.c
@@ -18,6 +18,13 @@ struct swap_cgroup {
};
#define SC_PER_PAGE (PAGE_SIZE/sizeof(struct swap_cgroup))
+struct swap_cgroup_iter {
+ struct swap_cgroup_ctrl *ctrl;
+ struct swap_cgroup *sc;
+ swp_entry_t entry;
+ unsigned long flags;
+};
+
/*
* SwapCgroup implements "lookup" and "exchange" operations.
* In typical usage, this swap_cgroup is accessed via memcg's charge/uncharge
@@ -75,6 +82,34 @@ static struct swap_cgroup *lookup_swap_cgroup(swp_entry_t
ent,
return sc + offset % SC_PER_PAGE;
}
+static void swap_cgroup_iter_init(struct swap_cgroup_iter *iter, swp_entry_t
ent)
+{
+ iter->entry = ent;
+ iter->sc = lookup_swap_cgroup(ent, &iter->ctrl);
+ spin_lock_irqsave(&iter->ctrl->lock, iter->flags);
+}
+
+static void swap_cgroup_iter_exit(struct swap_cgroup_iter *iter)
+{
+ spin_unlock_irqrestore(&iter->ctrl->lock, iter->flags);
+}
+
+/*
+ * swap_cgroup is stored in a kind of discontinuous array. That is,
+ * they are continuous in one page, but not across page boundary. And
+ * there is one lock for each page.
+ */
+static void swap_cgroup_iter_advance(struct swap_cgroup_iter *iter)
+{
+ iter->sc++;
+ iter->entry.val++;
+ if (!(((unsigned long)iter->sc) & PAGE_MASK)) {
+ spin_unlock_irqrestore(&iter->ctrl->lock, iter->flags);
+ iter->sc = lookup_swap_cgroup(iter->entry, &iter->ctrl);
+ spin_lock_irqsave(&iter->ctrl->lock, iter->flags);
+ }
+}
+
/**
* swap_cgroup_cmpxchg - cmpxchg mem_cgroup's id for this swp_entry.
* @ent: swap entry to be cmpxchged
@@ -87,20 +122,18 @@ static struct swap_cgroup *lookup_swap_cgroup(swp_entry_t
ent,
unsigned short swap_cgroup_cmpxchg(swp_entry_t ent,
unsigned short old, unsigned short new)
{
- struct swap_cgroup_ctrl *ctrl;
- struct swap_cgroup *sc;
- unsigned long flags;
+ struct swap_cgroup_iter iter;
unsigned short retval;
- sc = lookup_swap_cgroup(ent, &ctrl);
+ swap_cgroup_iter_init(&iter, ent);
- spin_lock_irqsave(&ctrl->lock, flags);
- retval = sc->id;
+ retval = iter.sc->id;
if (retval == old)
- sc->id = new;
+ iter.sc->id = new;
else
retval = 0;
- spin_unlock_irqrestore(&ctrl->lock, flags);
+
+ swap_cgroup_iter_exit(&iter);
return retval;
}
@@ -114,18 +147,15 @@ unsigned short swap_cgroup_cmpxchg(swp_entry_t ent,
*/
unsigned short swap_cgroup_record(swp_entry_t ent, unsigned short id)
{
- struct swap_cgroup_ctrl *ctrl;
- struct swap_cgroup *sc;
+ struct swap_cgroup_iter iter;
unsigned short old;
- unsigned long flags;
- sc = lookup_swap_cgroup(ent, &ctrl);
+ swap_cgroup_iter_init(&iter, ent);
- spin_lock_irqsave(&ctrl->lock, flags);
- old = sc->id;
- sc->id = id;
- spin_unlock_irqrestore(&ctrl->lock, flags);
+ old = iter.sc->id;
+ iter.sc->id = id;
+ swap_cgroup_iter_exit(&iter);
return old;
}
--
2.8.1
