mm: move memcg hierarchy reclaim to generic reclaim code
Memory cgroup limit reclaim and traditional global pressure reclaim will
soon share the same code to reclaim from a hierarchical tree of memory
cgroups.
In preparation of this, move the two right next to each other in
shrink_zone().
The mem_cgroup_hierarchical_reclaim() polymath is split into a soft
limit reclaim function, which still does hierarchy walking on its own,
and a limit (shrinking) reclaim function, which relies on generic
reclaim code to walk the hierarchy.
Signed-off-by: Johannes Weiner <jweiner@redhat.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Ying Han <yinghan@google.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Hugh Dickins <hughd@google.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 bec451d..750ed14 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -370,8 +370,6 @@
#define MEM_CGROUP_RECLAIM_NOSWAP (1 << MEM_CGROUP_RECLAIM_NOSWAP_BIT)
#define MEM_CGROUP_RECLAIM_SHRINK_BIT 0x1
#define MEM_CGROUP_RECLAIM_SHRINK (1 << MEM_CGROUP_RECLAIM_SHRINK_BIT)
-#define MEM_CGROUP_RECLAIM_SOFT_BIT 0x2
-#define MEM_CGROUP_RECLAIM_SOFT (1 << MEM_CGROUP_RECLAIM_SOFT_BIT)
static void mem_cgroup_get(struct mem_cgroup *memcg);
static void mem_cgroup_put(struct mem_cgroup *memcg);
@@ -857,20 +855,33 @@
return memcg;
}
-struct mem_cgroup_reclaim_cookie {
- struct zone *zone;
- int priority;
- unsigned int generation;
-};
-
-static struct mem_cgroup *
-mem_cgroup_iter(struct mem_cgroup *root,
- struct mem_cgroup *prev,
- struct mem_cgroup_reclaim_cookie *reclaim)
+/**
+ * mem_cgroup_iter - iterate over memory cgroup hierarchy
+ * @root: hierarchy root
+ * @prev: previously returned memcg, NULL on first invocation
+ * @reclaim: cookie for shared reclaim walks, NULL for full walks
+ *
+ * Returns references to children of the hierarchy below @root, or
+ * @root itself, or %NULL after a full round-trip.
+ *
+ * Caller must pass the return value in @prev on subsequent
+ * invocations for reference counting, or use mem_cgroup_iter_break()
+ * to cancel a hierarchy walk before the round-trip is complete.
+ *
+ * Reclaimers can specify a zone and a priority level in @reclaim to
+ * divide up the memcgs in the hierarchy among all concurrent
+ * reclaimers operating on the same zone and priority.
+ */
+struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
+ struct mem_cgroup *prev,
+ struct mem_cgroup_reclaim_cookie *reclaim)
{
struct mem_cgroup *memcg = NULL;
int id = 0;
+ if (mem_cgroup_disabled())
+ return NULL;
+
if (!root)
root = root_mem_cgroup;
@@ -926,8 +937,13 @@
return memcg;
}
-static void mem_cgroup_iter_break(struct mem_cgroup *root,
- struct mem_cgroup *prev)
+/**
+ * mem_cgroup_iter_break - abort a hierarchy walk prematurely
+ * @root: hierarchy root
+ * @prev: last visited hierarchy member as returned by mem_cgroup_iter()
+ */
+void mem_cgroup_iter_break(struct mem_cgroup *root,
+ struct mem_cgroup *prev)
{
if (!root)
root = root_mem_cgroup;
@@ -1555,6 +1571,42 @@
return min(limit, memsw);
}
+static unsigned long mem_cgroup_reclaim(struct mem_cgroup *memcg,
+ gfp_t gfp_mask,
+ unsigned long flags)
+{
+ unsigned long total = 0;
+ bool noswap = false;
+ int loop;
+
+ if (flags & MEM_CGROUP_RECLAIM_NOSWAP)
+ noswap = true;
+ if (!(flags & MEM_CGROUP_RECLAIM_SHRINK) && memcg->memsw_is_minimum)
+ noswap = true;
+
+ for (loop = 0; loop < MEM_CGROUP_MAX_RECLAIM_LOOPS; loop++) {
+ if (loop)
+ drain_all_stock_async(memcg);
+ total += try_to_free_mem_cgroup_pages(memcg, gfp_mask, noswap);
+ /*
+ * Allow limit shrinkers, which are triggered directly
+ * by userspace, to catch signals and stop reclaim
+ * after minimal progress, regardless of the margin.
+ */
+ if (total && (flags & MEM_CGROUP_RECLAIM_SHRINK))
+ break;
+ if (mem_cgroup_margin(memcg))
+ break;
+ /*
+ * If nothing was reclaimed after two attempts, there
+ * may be no reclaimable pages in this hierarchy.
+ */
+ if (loop && !total)
+ break;
+ }
+ return total;
+}
+
/**
* test_mem_cgroup_node_reclaimable
* @mem: the target memcg
@@ -1692,30 +1744,14 @@
}
#endif
-/*
- * Scan the hierarchy if needed to reclaim memory. We remember the last child
- * we reclaimed from, so that we don't end up penalizing one child extensively
- * based on its position in the children list.
- *
- * root_memcg is the original ancestor that we've been reclaim from.
- *
- * We give up and return to the caller when we visit root_memcg twice.
- * (other groups can be removed while we're walking....)
- *
- * If shrink==true, for avoiding to free too much, this returns immedieately.
- */
-static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_memcg,
- struct zone *zone,
- gfp_t gfp_mask,
- unsigned long reclaim_options,
- unsigned long *total_scanned)
+static int mem_cgroup_soft_reclaim(struct mem_cgroup *root_memcg,
+ struct zone *zone,
+ gfp_t gfp_mask,
+ unsigned long *total_scanned)
{
struct mem_cgroup *victim = NULL;
- int ret, total = 0;
+ int total = 0;
int loop = 0;
- bool noswap = reclaim_options & MEM_CGROUP_RECLAIM_NOSWAP;
- bool shrink = reclaim_options & MEM_CGROUP_RECLAIM_SHRINK;
- bool check_soft = reclaim_options & MEM_CGROUP_RECLAIM_SOFT;
unsigned long excess;
unsigned long nr_scanned;
struct mem_cgroup_reclaim_cookie reclaim = {
@@ -1725,29 +1761,17 @@
excess = res_counter_soft_limit_excess(&root_memcg->res) >> PAGE_SHIFT;
- /* If memsw_is_minimum==1, swap-out is of-no-use. */
- if (!check_soft && !shrink && root_memcg->memsw_is_minimum)
- noswap = true;
-
while (1) {
victim = mem_cgroup_iter(root_memcg, victim, &reclaim);
if (!victim) {
loop++;
- /*
- * We are not draining per cpu cached charges during
- * soft limit reclaim because global reclaim doesn't
- * care about charges. It tries to free some memory and
- * charges will not give any.
- */
- if (!check_soft && loop >= 1)
- drain_all_stock_async(root_memcg);
if (loop >= 2) {
/*
* If we have not been able to reclaim
* anything, it might because there are
* no reclaimable pages under this hierarchy
*/
- if (!check_soft || !total)
+ if (!total)
break;
/*
* We want to do more targeted reclaim.
@@ -1761,30 +1785,12 @@
}
continue;
}
- if (!mem_cgroup_reclaimable(victim, noswap)) {
- /* this cgroup's local usage == 0 */
+ if (!mem_cgroup_reclaimable(victim, false))
continue;
- }
- /* we use swappiness of local cgroup */
- if (check_soft) {
- ret = mem_cgroup_shrink_node_zone(victim, gfp_mask,
- noswap, zone, &nr_scanned);
- *total_scanned += nr_scanned;
- } else
- ret = try_to_free_mem_cgroup_pages(victim, gfp_mask,
- noswap);
- total += ret;
- /*
- * At shrinking usage, we can't check we should stop here or
- * reclaim more. It's depends on callers. last_scanned_child
- * will work enough for keeping fairness under tree.
- */
- if (shrink)
- break;
- if (check_soft) {
- if (!res_counter_soft_limit_excess(&root_memcg->res))
- break;
- } else if (mem_cgroup_margin(root_memcg))
+ total += mem_cgroup_shrink_node_zone(victim, gfp_mask, false,
+ zone, &nr_scanned);
+ *total_scanned += nr_scanned;
+ if (!res_counter_soft_limit_excess(&root_memcg->res))
break;
}
mem_cgroup_iter_break(root_memcg, victim);
@@ -2281,8 +2287,7 @@
if (!(gfp_mask & __GFP_WAIT))
return CHARGE_WOULDBLOCK;
- ret = mem_cgroup_hierarchical_reclaim(mem_over_limit, NULL,
- gfp_mask, flags, NULL);
+ ret = mem_cgroup_reclaim(mem_over_limit, gfp_mask, flags);
if (mem_cgroup_margin(mem_over_limit) >= nr_pages)
return CHARGE_RETRY;
/*
@@ -3559,9 +3564,8 @@
if (!ret)
break;
- mem_cgroup_hierarchical_reclaim(memcg, NULL, GFP_KERNEL,
- MEM_CGROUP_RECLAIM_SHRINK,
- NULL);
+ mem_cgroup_reclaim(memcg, GFP_KERNEL,
+ MEM_CGROUP_RECLAIM_SHRINK);
curusage = res_counter_read_u64(&memcg->res, RES_USAGE);
/* Usage is reduced ? */
if (curusage >= oldusage)
@@ -3619,10 +3623,9 @@
if (!ret)
break;
- mem_cgroup_hierarchical_reclaim(memcg, NULL, GFP_KERNEL,
- MEM_CGROUP_RECLAIM_NOSWAP |
- MEM_CGROUP_RECLAIM_SHRINK,
- NULL);
+ mem_cgroup_reclaim(memcg, GFP_KERNEL,
+ MEM_CGROUP_RECLAIM_NOSWAP |
+ MEM_CGROUP_RECLAIM_SHRINK);
curusage = res_counter_read_u64(&memcg->memsw, RES_USAGE);
/* Usage is reduced ? */
if (curusage >= oldusage)
@@ -3665,10 +3668,8 @@
break;
nr_scanned = 0;
- reclaimed = mem_cgroup_hierarchical_reclaim(mz->mem, zone,
- gfp_mask,
- MEM_CGROUP_RECLAIM_SOFT,
- &nr_scanned);
+ reclaimed = mem_cgroup_soft_reclaim(mz->mem, zone,
+ gfp_mask, &nr_scanned);
nr_reclaimed += reclaimed;
*total_scanned += nr_scanned;
spin_lock(&mctz->lock);