* + mm-memcg-disable-threshold-event-handlers-on-preempt_rt.patch added to -mm tree
@ 2022-02-17 21:13 Andrew Morton
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Morton @ 2022-02-17 21:13 UTC (permalink / raw)
To: mm-commits, vdavydov.dev, tglx, shakeelb, peterz, oliver.sang,
mkoutny, mhocko, mhocko, longman, hannes, guro, bigeasy, akpm
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 5209 bytes --]
The patch titled
Subject: mm/memcg: disable threshold event handlers on PREEMPT_RT
has been added to the -mm tree. Its filename is
mm-memcg-disable-threshold-event-handlers-on-preempt_rt.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-memcg-disable-threshold-event-handlers-on-preempt_rt.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-memcg-disable-threshold-event-handlers-on-preempt_rt.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: 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/20220217094802.3644569-3-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Suggested-by: Michal Hocko <mhocko@kernel.org>
Suggested-by: Michal Koutný <mkoutny@suse.com>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: kernel test robot <oliver.sang@intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shakeel Butt <shakeelb@google.com>
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>
---
Documentation/admin-guide/cgroup-v1/memory.rst | 2 ++
mm/memcontrol.c | 14 ++++++++++++--
2 files changed, 14 insertions(+), 2 deletions(-)
--- a/Documentation/admin-guide/cgroup-v1/memory.rst~mm-memcg-disable-threshold-event-handlers-on-preempt_rt
+++ a/Documentation/admin-guide/cgroup-v1/memory.rst
@@ -64,6 +64,7 @@ Brief summary of control files.
threads
cgroup.procs show list of processes
cgroup.event_control an interface for event_fd()
+ This knob is not available on CONFIG_PREEMPT_RT systems.
memory.usage_in_bytes show current usage for memory
(See 5.5 for details)
memory.memsw.usage_in_bytes show current usage for memory+Swap
@@ -75,6 +76,7 @@ Brief summary of control files.
memory.max_usage_in_bytes show max memory usage recorded
memory.memsw.max_usage_in_bytes show max memory+Swap usage recorded
memory.soft_limit_in_bytes set/show soft limit of memory usage
+ This knob is not available on CONFIG_PREEMPT_RT systems.
memory.stat show various statistics
memory.use_hierarchy set/show hierarchical account enabled
This knob is deprecated and shouldn't be
--- a/mm/memcontrol.c~mm-memcg-disable-threshold-event-handlers-on-preempt_rt
+++ a/mm/memcontrol.c
@@ -858,6 +858,9 @@ static bool mem_cgroup_event_ratelimit(s
*/
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 k
}
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
char *endp;
int ret;
+ if (IS_ENABLED(CONFIG_PREEMPT_RT))
+ return -EOPNOTSUPP;
+
buf = strstrip(buf);
efd = simple_strtoul(buf, &endp, 10);
_
Patches currently in -mm which might be from bigeasy@linutronix.de are
mm-memcg-disable-threshold-event-handlers-on-preempt_rt.patch
mm-memcg-protect-per-cpu-counter-by-disabling-preemption-on-preempt_rt-where-needed.patch
mm-memcg-protect-memcg_stock-with-a-local_lock_t.patch
^ permalink raw reply [flat|nested] 2+ messages in thread* + mm-memcg-disable-threshold-event-handlers-on-preempt_rt.patch added to -mm tree
@ 2022-02-21 19:26 Andrew Morton
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Morton @ 2022-02-21 19:26 UTC (permalink / raw)
To: mm-commits, vdavydov.dev, tglx, shakeelb, peterz, oliver.sang,
mkoutny, mhocko, mhocko, longman, hannes, guro, bigeasy, akpm
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 5297 bytes --]
The patch titled
Subject: mm/memcg: disable threshold event handlers on PREEMPT_RT
has been added to the -mm tree. Its filename is
mm-memcg-disable-threshold-event-handlers-on-preempt_rt.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-memcg-disable-threshold-event-handlers-on-preempt_rt.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-memcg-disable-threshold-event-handlers-on-preempt_rt.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: 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/20220221182540.380526-3-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Suggested-by: Michal Hocko <mhocko@kernel.org>
Suggested-by: Michal Koutný <mkoutny@suse.com>
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>
---
Documentation/admin-guide/cgroup-v1/memory.rst | 2 ++
mm/memcontrol.c | 14 ++++++++++++--
2 files changed, 14 insertions(+), 2 deletions(-)
--- a/Documentation/admin-guide/cgroup-v1/memory.rst~mm-memcg-disable-threshold-event-handlers-on-preempt_rt
+++ a/Documentation/admin-guide/cgroup-v1/memory.rst
@@ -64,6 +64,7 @@ Brief summary of control files.
threads
cgroup.procs show list of processes
cgroup.event_control an interface for event_fd()
+ This knob is not available on CONFIG_PREEMPT_RT systems.
memory.usage_in_bytes show current usage for memory
(See 5.5 for details)
memory.memsw.usage_in_bytes show current usage for memory+Swap
@@ -75,6 +76,7 @@ Brief summary of control files.
memory.max_usage_in_bytes show max memory usage recorded
memory.memsw.max_usage_in_bytes show max memory+Swap usage recorded
memory.soft_limit_in_bytes set/show soft limit of memory usage
+ This knob is not available on CONFIG_PREEMPT_RT systems.
memory.stat show various statistics
memory.use_hierarchy set/show hierarchical account enabled
This knob is deprecated and shouldn't be
--- a/mm/memcontrol.c~mm-memcg-disable-threshold-event-handlers-on-preempt_rt
+++ a/mm/memcontrol.c
@@ -858,6 +858,9 @@ static bool mem_cgroup_event_ratelimit(s
*/
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 k
}
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
char *endp;
int ret;
+ if (IS_ENABLED(CONFIG_PREEMPT_RT))
+ return -EOPNOTSUPP;
+
buf = strstrip(buf);
efd = simple_strtoul(buf, &endp, 10);
_
Patches currently in -mm which might be from bigeasy@linutronix.de are
mm-memcg-disable-threshold-event-handlers-on-preempt_rt.patch
mm-memcg-protect-per-cpu-counter-by-disabling-preemption-on-preempt_rt-where-needed.patch
mm-memcg-protect-memcg_stock-with-a-local_lock_t.patch
mm-memcg-disable-migration-instead-of-preemption-in-drain_all_stock.patch
^ permalink raw reply [flat|nested] 2+ messages in thread
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2022-02-21 19:26 Andrew Morton
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