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authorSebastian Andrzej Siewior <bigeasy@linutronix.de>2022-03-23 00:40:38 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2022-03-23 01:57:02 +0300
commit2343e88d238f5de973d609d861c505890f94f22e (patch)
treeaf09354cbd41201f5c41329d0f99960a2d66f24a /mm/memcontrol.c
parentfead2b869764f89d524b79dc8862e61d5191be55 (diff)
downloadlinux-2343e88d238f5de973d609d861c505890f94f22e.tar.xz
mm/memcg: disable threshold event handlers on PREEMPT_RT
During the integration of PREEMPT_RT support, the code flow around memcg_check_events() resulted in `twisted code'. Moving the code around and avoiding then would then lead to an additional local-irq-save section within memcg_check_events(). While looking better, it adds a local-irq-save section to code flow which is usually within an local-irq-off block on non-PREEMPT_RT configurations. The threshold event handler is a deprecated memcg v1 feature. Instead of trying to get it to work under PREEMPT_RT just disable it. There should be no users on PREEMPT_RT. From that perspective it makes even less sense to get it to work under PREEMPT_RT while having zero users. Make memory.soft_limit_in_bytes and cgroup.event_control return -EOPNOTSUPP on PREEMPT_RT. Make an empty memcg_check_events() and memcg_write_event_control() which return only -EOPNOTSUPP on PREEMPT_RT. Document that the two knobs are disabled on PREEMPT_RT. Link: https://lkml.kernel.org/r/20220226204144.1008339-3-bigeasy@linutronix.de Suggested-by: Michal Hocko <mhocko@kernel.org> Suggested-by: Michal Koutný <mkoutny@suse.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Acked-by: Roman Gushchin <guro@fb.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Shakeel Butt <shakeelb@google.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: kernel test robot <oliver.sang@intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Waiman Long <longman@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memcontrol.c')
-rw-r--r--mm/memcontrol.c14
1 files changed, 12 insertions, 2 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7bf204b2b053..6c61b4ec041e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -858,6 +858,9 @@ static bool mem_cgroup_event_ratelimit(struct mem_cgroup *memcg,
*/
static void memcg_check_events(struct mem_cgroup *memcg, int nid)
{
+ if (IS_ENABLED(CONFIG_PREEMPT_RT))
+ return;
+
/* threshold event is triggered in finer grain than soft limit */
if (unlikely(mem_cgroup_event_ratelimit(memcg,
MEM_CGROUP_TARGET_THRESH))) {
@@ -3731,8 +3734,12 @@ static ssize_t mem_cgroup_write(struct kernfs_open_file *of,
}
break;
case RES_SOFT_LIMIT:
- memcg->soft_limit = nr_pages;
- ret = 0;
+ if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
+ ret = -EOPNOTSUPP;
+ } else {
+ memcg->soft_limit = nr_pages;
+ ret = 0;
+ }
break;
}
return ret ?: nbytes;
@@ -4708,6 +4715,9 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of,
char *endp;
int ret;
+ if (IS_ENABLED(CONFIG_PREEMPT_RT))
+ return -EOPNOTSUPP;
+
buf = strstrip(buf);
efd = simple_strtoul(buf, &endp, 10);