[PATCH] mm: vmscan: protect shrinker idr replace with CONFIG_MEMCG

Subsystems: memory management, memory management - mglru (multi-gen lru), memory management - reclaim, the rest

STALE2507d

8 messages, 3 authors, 2019-12-05 · open the first message on its own page

[PATCH] mm: vmscan: protect shrinker idr replace with CONFIG_MEMCG

From: Yang Shi <hidden>
Date: 2019-12-04 19:16:31 

Since commit 0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 ("mm: shrinker:
make shrinker not depend on memcg kmem"), shrinkers' idr is protected by
CONFIG_MEMCG instead of CONFIG_MEMCG_KMEM, so it makes no sense to
protect shrinker idr replace with CONFIG_MEMCG_KMEM.

Cc: Kirill Tkhai <redacted>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Shakeel Butt <redacted>
Cc: Roman Gushchin <redacted>
Signed-off-by: Yang Shi <redacted>
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index ee4eecc..e7f10c4 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -422,7 +422,7 @@ void register_shrinker_prepared(struct shrinker *shrinker)
 {
 	down_write(&shrinker_rwsem);
 	list_add_tail(&shrinker->list, &shrinker_list);
-#ifdef CONFIG_MEMCG_KMEM
+#ifdef CONFIG_MEMCG
 	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
 		idr_replace(&shrinker_idr, shrinker, shrinker->id);
 #endif
-- 
1.8.3.1

Re: [PATCH] mm: vmscan: protect shrinker idr replace with CONFIG_MEMCG

From: Kirill Tkhai <hidden>
Date: 2019-12-05 08:23:57 

On 04.12.2019 22:16, Yang Shi wrote:
Since commit 0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 ("mm: shrinker:
make shrinker not depend on memcg kmem"), shrinkers' idr is protected by
CONFIG_MEMCG instead of CONFIG_MEMCG_KMEM, so it makes no sense to
protect shrinker idr replace with CONFIG_MEMCG_KMEM.

Cc: Kirill Tkhai <redacted>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Shakeel Butt <redacted>
Cc: Roman Gushchin <redacted>
Signed-off-by: Yang Shi <redacted>
It looks like that in CONFIG_SLOB case we do not even call some shrinkers
for subordinate mem cgroups (i.e., we don't call deferred_split_shrinker),
since they never become completely registered.

Fixes: 0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 ("mm: shrinker: make shrinker not depend on memcg kmem")
Reviewed-by: Kirill Tkhai <redacted>
quoted hunk
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index ee4eecc..e7f10c4 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -422,7 +422,7 @@ void register_shrinker_prepared(struct shrinker *shrinker)
 {
 	down_write(&shrinker_rwsem);
 	list_add_tail(&shrinker->list, &shrinker_list);
-#ifdef CONFIG_MEMCG_KMEM
+#ifdef CONFIG_MEMCG
 	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
 		idr_replace(&shrinker_idr, shrinker, shrinker->id);
 #endif





  

    
Re: [PATCH] mm: vmscan: protect shrinker idr replace with CONFIG_MEMCG

    

      From: Michal Hocko <mhocko@kernel.org>

      Date: 2019-12-05 09:43:47 
    

  

  
On Thu 05-12-19 11:23:28, Kirill Tkhai wrote:
On 04.12.2019 22:16, Yang Shi wrote:
quoted
Since commit 0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 ("mm: shrinker:
make shrinker not depend on memcg kmem"), shrinkers' idr is protected by
CONFIG_MEMCG instead of CONFIG_MEMCG_KMEM, so it makes no sense to
protect shrinker idr replace with CONFIG_MEMCG_KMEM.

Cc: Kirill Tkhai <redacted>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Shakeel Butt <redacted>
Cc: Roman Gushchin <redacted>
Signed-off-by: Yang Shi <redacted>
It looks like that in CONFIG_SLOB case we do not even call some shrinkers
for subordinate mem cgroups (i.e., we don't call deferred_split_shrinker),
since they never become completely registered.

Fixes: 0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 ("mm: shrinker: make shrinker not depend on memcg kmem")
I am confused. Why the Fixes tag? Nothing should be really broken with
KMEM config guard right?

This is a mere clean up AFAICS.

Reviewed-by: Kirill Tkhai <redacted>

quoted
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index ee4eecc..e7f10c4 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -422,7 +422,7 @@ void register_shrinker_prepared(struct shrinker *shrinker)
 {
 	down_write(&shrinker_rwsem);
 	list_add_tail(&shrinker->list, &shrinker_list);
-#ifdef CONFIG_MEMCG_KMEM
+#ifdef CONFIG_MEMCG
 	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
 		idr_replace(&shrinker_idr, shrinker, shrinker->id);
 #endif
-- 
Michal Hocko
SUSE Labs






  

    
Re: [PATCH] mm: vmscan: protect shrinker idr replace with CONFIG_MEMCG

    

      From: Michal Hocko <mhocko@kernel.org>

      Date: 2019-12-05 09:44:06 
    

  

  
On Thu 05-12-19 03:16:18, Yang Shi wrote:
Since commit 0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 ("mm: shrinker:
make shrinker not depend on memcg kmem"), shrinkers' idr is protected by
CONFIG_MEMCG instead of CONFIG_MEMCG_KMEM, so it makes no sense to
protect shrinker idr replace with CONFIG_MEMCG_KMEM.

Cc: Kirill Tkhai <redacted>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Shakeel Butt <redacted>
Cc: Roman Gushchin <redacted>
Signed-off-by: Yang Shi <redacted>
Acked-by: Michal Hocko <mhocko@suse.com>

quoted hunk
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index ee4eecc..e7f10c4 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -422,7 +422,7 @@ void register_shrinker_prepared(struct shrinker *shrinker)
 {
 	down_write(&shrinker_rwsem);
 	list_add_tail(&shrinker->list, &shrinker_list);
-#ifdef CONFIG_MEMCG_KMEM
+#ifdef CONFIG_MEMCG
 	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
 		idr_replace(&shrinker_idr, shrinker, shrinker->id);
 #endif
-- 
1.8.3.1
-- 
Michal Hocko
SUSE Labs






  

    
Re: [PATCH] mm: vmscan: protect shrinker idr replace with CONFIG_MEMCG

    

      From: Kirill Tkhai <hidden>

      Date: 2019-12-05 10:00:44 
    

  

  
On 05.12.2019 12:43, Michal Hocko wrote:
On Thu 05-12-19 11:23:28, Kirill Tkhai wrote:
quoted
On 04.12.2019 22:16, Yang Shi wrote:
quoted
Since commit 0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 ("mm: shrinker:
make shrinker not depend on memcg kmem"), shrinkers' idr is protected by
CONFIG_MEMCG instead of CONFIG_MEMCG_KMEM, so it makes no sense to
protect shrinker idr replace with CONFIG_MEMCG_KMEM.

Cc: Kirill Tkhai <redacted>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Shakeel Butt <redacted>
Cc: Roman Gushchin <redacted>
Signed-off-by: Yang Shi <redacted>
It looks like that in CONFIG_SLOB case we do not even call some shrinkers
for subordinate mem cgroups (i.e., we don't call deferred_split_shrinker),
since they never become completely registered.

Fixes: 0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 ("mm: shrinker: make shrinker not depend on memcg kmem")
I am confused. Why the Fixes tag? Nothing should be really broken with
KMEM config guard right?
idr_replace() is disabled in CONFIG_MEMCG && CONFIG_SLOB case, and this is
wrong.

0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 goes in the series, which enables
shrinker_idr infrastructure for huge_memory.c's deferred_split_shrinker
in CONFIG_MEMCG case. Previously, all SHRINKER_MEMCG_AWARE shrinkers were
based on LRUs, and they remain to base of CONFIG_MEMCG_KMEM.
But deferred_split_shrinker is an exception.

In CONFIG_MEMCG && CONFIG_SLOB case, shrinker_idr contains only shrinker,
and it is deferred_split_shrinker. But it is never actually called, since
idr_replace() is never compiled. deferred_split_shrinker all the time is
staying in half-registered state, and it's never called for subordinate
mem cgroups.

So, this is a BUG, and this should go to stable.

This is a mere clean up AFAICS.

quoted
Reviewed-by: Kirill Tkhai <redacted>

quoted
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index ee4eecc..e7f10c4 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -422,7 +422,7 @@ void register_shrinker_prepared(struct shrinker *shrinker)
 {
 	down_write(&shrinker_rwsem);
 	list_add_tail(&shrinker->list, &shrinker_list);
-#ifdef CONFIG_MEMCG_KMEM
+#ifdef CONFIG_MEMCG
 	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
 		idr_replace(&shrinker_idr, shrinker, shrinker->id);
 #endif





  

    
Re: [PATCH] mm: vmscan: protect shrinker idr replace with CONFIG_MEMCG

    

      From: Kirill Tkhai <hidden>

      Date: 2019-12-05 10:11:29 
    

  

  
On 05.12.2019 13:00, Kirill Tkhai wrote:
On 05.12.2019 12:43, Michal Hocko wrote:
quoted
On Thu 05-12-19 11:23:28, Kirill Tkhai wrote:
quoted
On 04.12.2019 22:16, Yang Shi wrote:
quoted
Since commit 0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 ("mm: shrinker:
make shrinker not depend on memcg kmem"), shrinkers' idr is protected by
CONFIG_MEMCG instead of CONFIG_MEMCG_KMEM, so it makes no sense to
protect shrinker idr replace with CONFIG_MEMCG_KMEM.

Cc: Kirill Tkhai <redacted>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Shakeel Butt <redacted>
Cc: Roman Gushchin <redacted>
Signed-off-by: Yang Shi <redacted>
It looks like that in CONFIG_SLOB case we do not even call some shrinkers
for subordinate mem cgroups (i.e., we don't call deferred_split_shrinker),
since they never become completely registered.

Fixes: 0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 ("mm: shrinker: make shrinker not depend on memcg kmem")
I am confused. Why the Fixes tag? Nothing should be really broken with
KMEM config guard right?
idr_replace() is disabled in CONFIG_MEMCG && CONFIG_SLOB case, and this is
wrong.

0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 goes in the series, which enables
shrinker_idr infrastructure for huge_memory.c's deferred_split_shrinker
in CONFIG_MEMCG case. Previously, all SHRINKER_MEMCG_AWARE shrinkers were
based on LRUs, and they remain to base of CONFIG_MEMCG_KMEM.
But deferred_split_shrinker is an exception.

In CONFIG_MEMCG && CONFIG_SLOB case, shrinker_idr contains only shrinker,
and it is deferred_split_shrinker. But it is never actually called, since
idr_replace() is never compiled. deferred_split_shrinker all the time is
staying in half-registered state, and it's never called for subordinate
mem cgroups.

So, this is a BUG, and this should go to stable.
The visible effect is that deferred_split_shrinker is never called
from shrink_slab() for subordinate mem cgroups. It's called only
for root_mem_cgroup.

quoted
This is a mere clean up AFAICS.

quoted
Reviewed-by: Kirill Tkhai <redacted>

quoted
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index ee4eecc..e7f10c4 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -422,7 +422,7 @@ void register_shrinker_prepared(struct shrinker *shrinker)
 {
 	down_write(&shrinker_rwsem);
 	list_add_tail(&shrinker->list, &shrinker_list);
-#ifdef CONFIG_MEMCG_KMEM
+#ifdef CONFIG_MEMCG
 	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
 		idr_replace(&shrinker_idr, shrinker, shrinker->id);
 #endif





  

    
Re: [PATCH] mm: vmscan: protect shrinker idr replace with CONFIG_MEMCG

    

      From: Michal Hocko <mhocko@kernel.org>

      Date: 2019-12-05 11:45:27 
    

  

  
On Thu 05-12-19 13:00:31, Kirill Tkhai wrote:
On 05.12.2019 12:43, Michal Hocko wrote:
quoted
On Thu 05-12-19 11:23:28, Kirill Tkhai wrote:
quoted
On 04.12.2019 22:16, Yang Shi wrote:
quoted
Since commit 0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 ("mm: shrinker:
make shrinker not depend on memcg kmem"), shrinkers' idr is protected by
CONFIG_MEMCG instead of CONFIG_MEMCG_KMEM, so it makes no sense to
protect shrinker idr replace with CONFIG_MEMCG_KMEM.

Cc: Kirill Tkhai <redacted>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Shakeel Butt <redacted>
Cc: Roman Gushchin <redacted>
Signed-off-by: Yang Shi <redacted>
It looks like that in CONFIG_SLOB case we do not even call some shrinkers
for subordinate mem cgroups (i.e., we don't call deferred_split_shrinker),
since they never become completely registered.

Fixes: 0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 ("mm: shrinker: make shrinker not depend on memcg kmem")
I am confused. Why the Fixes tag? Nothing should be really broken with
KMEM config guard right?
idr_replace() is disabled in CONFIG_MEMCG && CONFIG_SLOB case, and this is
wrong.

0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 goes in the series, which enables
shrinker_idr infrastructure for huge_memory.c's deferred_split_shrinker
in CONFIG_MEMCG case. Previously, all SHRINKER_MEMCG_AWARE shrinkers were
based on LRUs, and they remain to base of CONFIG_MEMCG_KMEM.
But deferred_split_shrinker is an exception.

In CONFIG_MEMCG && CONFIG_SLOB case, shrinker_idr contains only shrinker,
and it is deferred_split_shrinker. But it is never actually called, since
idr_replace() is never compiled. deferred_split_shrinker all the time is
staying in half-registered state, and it's never called for subordinate
mem cgroups.

So, this is a BUG, and this should go to stable.
OK, I see. The changelog should describe all that. Thanks for the
clarification.

quoted
This is a mere clean up AFAICS.

quoted
Reviewed-by: Kirill Tkhai <redacted>

quoted
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index ee4eecc..e7f10c4 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -422,7 +422,7 @@ void register_shrinker_prepared(struct shrinker *shrinker)
 {
 	down_write(&shrinker_rwsem);
 	list_add_tail(&shrinker->list, &shrinker_list);
-#ifdef CONFIG_MEMCG_KMEM
+#ifdef CONFIG_MEMCG
 	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
 		idr_replace(&shrinker_idr, shrinker, shrinker->id);
 #endif
-- 
Michal Hocko
SUSE Labs






  

    
Re: [PATCH] mm: vmscan: protect shrinker idr replace with CONFIG_MEMCG

    

      From: Yang Shi <hidden>

      Date: 2019-12-05 17:05:23 
    

  

  

On 12/5/19 2:11 AM, Kirill Tkhai wrote:
On 05.12.2019 13:00, Kirill Tkhai wrote:
quoted
On 05.12.2019 12:43, Michal Hocko wrote:
quoted
On Thu 05-12-19 11:23:28, Kirill Tkhai wrote:
quoted
On 04.12.2019 22:16, Yang Shi wrote:
quoted
Since commit 0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 ("mm: shrinker:
make shrinker not depend on memcg kmem"), shrinkers' idr is protected by
CONFIG_MEMCG instead of CONFIG_MEMCG_KMEM, so it makes no sense to
protect shrinker idr replace with CONFIG_MEMCG_KMEM.

Cc: Kirill Tkhai <redacted>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Shakeel Butt <redacted>
Cc: Roman Gushchin <redacted>
Signed-off-by: Yang Shi <redacted>
It looks like that in CONFIG_SLOB case we do not even call some shrinkers
for subordinate mem cgroups (i.e., we don't call deferred_split_shrinker),
since they never become completely registered.

Fixes: 0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 ("mm: shrinker: make shrinker not depend on memcg kmem")
I am confused. Why the Fixes tag? Nothing should be really broken with
KMEM config guard right?
idr_replace() is disabled in CONFIG_MEMCG && CONFIG_SLOB case, and this is
wrong.

0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 goes in the series, which enables
shrinker_idr infrastructure for huge_memory.c's deferred_split_shrinker
in CONFIG_MEMCG case. Previously, all SHRINKER_MEMCG_AWARE shrinkers were
based on LRUs, and they remain to base of CONFIG_MEMCG_KMEM.
But deferred_split_shrinker is an exception.

In CONFIG_MEMCG && CONFIG_SLOB case, shrinker_idr contains only shrinker,
and it is deferred_split_shrinker. But it is never actually called, since
idr_replace() is never compiled. deferred_split_shrinker all the time is
staying in half-registered state, and it's never called for subordinate
mem cgroups.

So, this is a BUG, and this should go to stable.
The visible effect is that deferred_split_shrinker is never called
from shrink_slab() for subordinate mem cgroups. It's called only
for root_mem_cgroup.
Thanks for noticing the SLOB case, I didn't realize it and thought it was just a cleanup too.

Will update the information and cc to stable list for v2.

quoted
quoted
This is a mere clean up AFAICS.

quoted
Reviewed-by: Kirill Tkhai <redacted>

quoted
---
  mm/vmscan.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index ee4eecc..e7f10c4 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -422,7 +422,7 @@ void register_shrinker_prepared(struct shrinker *shrinker)
  {
  	down_write(&shrinker_rwsem);
  	list_add_tail(&shrinker->list, &shrinker_list);
-#ifdef CONFIG_MEMCG_KMEM
+#ifdef CONFIG_MEMCG
  	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
  		idr_replace(&shrinker_idr, shrinker, shrinker->id);
  #endif




    
  

  
    

      

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