The patch titled
Subject: memcontrol: add a new function to traverse online-only memcg hierarchy
has been added to the -mm mm-unstable branch. Its filename is
memcontrol-add-a-new-function-to-traverse-online-only-memcg-hierarchy.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/memcontrol-add-a-new-function-to-traverse-online-only-memcg-hierarchy.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Nhat Pham <nphamcs@xxxxxxxxx>
Subject: memcontrol: add a new function to traverse online-only memcg hierarchy
Date: Mon, 27 Nov 2023 15:45:56 -0800
The new zswap writeback scheme requires an online-only memcg hierarchy
traversal. Add this functionality via the new mem_cgroup_iter_online()
function - the old mem_cgroup_iter() is a special case of this new
function.
Link: https://lkml.kernel.org/r/20231127234600.2971029-3-nphamcs@xxxxxxxxx
Suggested-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Nhat Pham <nphamcs@xxxxxxxxx>
Cc: Chris Li <chrisl@xxxxxxxxxx>
Cc: Dan Streetman <ddstreet@xxxxxxxx>
Cc: Domenico Cerasuolo <cerasuolodomenico@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Cc: Seth Jennings <sjenning@xxxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: Vitaly Wool <vitaly.wool@xxxxxxxxxxxx>
Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/memcontrol.h | 13 +++++++++++++
mm/memcontrol.c | 29 +++++++++++++++++++++++++----
2 files changed, 38 insertions(+), 4 deletions(-)
--- a/include/linux/memcontrol.h~memcontrol-add-a-new-function-to-traverse-online-only-memcg-hierarchy
+++ a/include/linux/memcontrol.h
@@ -833,6 +833,10 @@ static inline void mem_cgroup_put(struct
struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *,
struct mem_cgroup *,
struct mem_cgroup_reclaim_cookie *);
+struct mem_cgroup *mem_cgroup_iter_online(struct mem_cgroup *root,
+ struct mem_cgroup *prev,
+ struct mem_cgroup_reclaim_cookie *reclaim,
+ bool online);
void mem_cgroup_iter_break(struct mem_cgroup *, struct mem_cgroup *);
void mem_cgroup_scan_tasks(struct mem_cgroup *memcg,
int (*)(struct task_struct *, void *), void *arg);
@@ -1385,6 +1389,15 @@ mem_cgroup_iter(struct mem_cgroup *root,
{
return NULL;
}
+
+static inline struct mem_cgroup *
+mem_cgroup_iter_online(struct mem_cgroup *root,
+ struct mem_cgroup *prev,
+ struct mem_cgroup_reclaim_cookie *reclaim,
+ bool online)
+{
+ return NULL;
+}
static inline void mem_cgroup_iter_break(struct mem_cgroup *root,
struct mem_cgroup *prev)
--- a/mm/memcontrol.c~memcontrol-add-a-new-function-to-traverse-online-only-memcg-hierarchy
+++ a/mm/memcontrol.c
@@ -1111,10 +1111,11 @@ again:
}
/**
- * mem_cgroup_iter - iterate over memory cgroup hierarchy
+ * mem_cgroup_iter_online - 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
+ * @online: whether to skip offline memcgs
*
* Returns references to children of the hierarchy below @root, or
* @root itself, or %NULL after a full round-trip.
@@ -1123,13 +1124,16 @@ again:
* invocations for reference counting, or use mem_cgroup_iter_break()
* to cancel a hierarchy walk before the round-trip is complete.
*
+ * Caller can skip offline memcgs by passing true for @online.
+ *
* Reclaimers can specify a node in @reclaim to divide up the memcgs
* in the hierarchy among all concurrent reclaimers operating on the
* same node.
*/
-struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
+struct mem_cgroup *mem_cgroup_iter_online(struct mem_cgroup *root,
struct mem_cgroup *prev,
- struct mem_cgroup_reclaim_cookie *reclaim)
+ struct mem_cgroup_reclaim_cookie *reclaim,
+ bool online)
{
struct mem_cgroup_reclaim_iter *iter;
struct cgroup_subsys_state *css = NULL;
@@ -1199,7 +1203,8 @@ struct mem_cgroup *mem_cgroup_iter(struc
* is provided by the caller, so we know it's alive
* and kicking, and don't take an extra reference.
*/
- if (css == &root->css || css_tryget(css)) {
+ if (css == &root->css || (!online && css_tryget(css)) ||
+ css_tryget_online(css)) {
memcg = mem_cgroup_from_css(css);
break;
}
@@ -1229,6 +1234,22 @@ out_unlock:
}
/**
+ * 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
+ *
+ * Perform an iteration on the memory cgroup hierarchy without skipping
+ * offline memcgs.
+ */
+struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
+ struct mem_cgroup *prev,
+ struct mem_cgroup_reclaim_cookie *reclaim)
+{
+ return mem_cgroup_iter_online(root, prev, reclaim, false);
+}
+
+/**
* mem_cgroup_iter_break - abort a hierarchy walk prematurely
* @root: hierarchy root
* @prev: last visited hierarchy member as returned by mem_cgroup_iter()
_
Patches currently in -mm which might be from nphamcs@xxxxxxxxx are
list_lru-allows-explicit-memcg-and-numa-node-selection.patch
memcontrol-add-a-new-function-to-traverse-online-only-memcg-hierarchy.patch
zswap-shrinks-zswap-pool-based-on-memory-pressure.patch
