* [PATCH -next] memcg: don't handle event_list for v2 when offlining
@ 2024-05-14 13:11 Xiu Jianfeng
2024-05-14 14:09 ` Michal Hocko
0 siblings, 1 reply; 5+ messages in thread
From: Xiu Jianfeng @ 2024-05-14 13:11 UTC (permalink / raw)
To: hannes, mhocko, roman.gushchin, shakeel.butt, muchun.song, akpm
Cc: cgroups, linux-mm, linux-kernel
The event_list for memcg is only valid for v1 and not used for v2,
so it's unnessesary to handle event_list for v2.
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
---
mm/memcontrol.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d127c9c5fabf..4254f9cd05f4 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5881,12 +5881,14 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
* Notify userspace about cgroup removing only after rmdir of cgroup
* directory to avoid race between userspace and kernelspace.
*/
- spin_lock_irq(&memcg->event_list_lock);
- list_for_each_entry_safe(event, tmp, &memcg->event_list, list) {
- list_del_init(&event->list);
- schedule_work(&event->remove);
+ if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
+ spin_lock_irq(&memcg->event_list_lock);
+ list_for_each_entry_safe(event, tmp, &memcg->event_list, list) {
+ list_del_init(&event->list);
+ schedule_work(&event->remove);
+ }
+ spin_unlock_irq(&memcg->event_list_lock);
}
- spin_unlock_irq(&memcg->event_list_lock);
page_counter_set_min(&memcg->memory, 0);
page_counter_set_low(&memcg->memory, 0);
--
2.34.1
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH -next] memcg: don't handle event_list for v2 when offlining
2024-05-14 13:11 [PATCH -next] memcg: don't handle event_list for v2 when offlining Xiu Jianfeng
@ 2024-05-14 14:09 ` Michal Hocko
2024-05-14 15:21 ` Roman Gushchin
2024-05-15 2:45 ` xiujianfeng
0 siblings, 2 replies; 5+ messages in thread
From: Michal Hocko @ 2024-05-14 14:09 UTC (permalink / raw)
To: Xiu Jianfeng
Cc: hannes, roman.gushchin, shakeel.butt, muchun.song, akpm, cgroups,
linux-mm, linux-kernel
On Tue 14-05-24 13:11:06, Xiu Jianfeng wrote:
> The event_list for memcg is only valid for v1 and not used for v2,
> so it's unnessesary to handle event_list for v2.
You are right but the code as is works just fine. The list will be
empty. It is true that we do not need to take event_list_lock lock but
nobody should be using this lock anyway. Also the offline callback is
not particularly hot path. So why do we want to change the code?
>
> Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
> ---
> mm/memcontrol.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index d127c9c5fabf..4254f9cd05f4 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5881,12 +5881,14 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
> * Notify userspace about cgroup removing only after rmdir of cgroup
> * directory to avoid race between userspace and kernelspace.
> */
> - spin_lock_irq(&memcg->event_list_lock);
> - list_for_each_entry_safe(event, tmp, &memcg->event_list, list) {
> - list_del_init(&event->list);
> - schedule_work(&event->remove);
> + if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
> + spin_lock_irq(&memcg->event_list_lock);
> + list_for_each_entry_safe(event, tmp, &memcg->event_list, list) {
> + list_del_init(&event->list);
> + schedule_work(&event->remove);
> + }
> + spin_unlock_irq(&memcg->event_list_lock);
> }
> - spin_unlock_irq(&memcg->event_list_lock);
>
> page_counter_set_min(&memcg->memory, 0);
> page_counter_set_low(&memcg->memory, 0);
> --
> 2.34.1
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH -next] memcg: don't handle event_list for v2 when offlining
2024-05-14 14:09 ` Michal Hocko
@ 2024-05-14 15:21 ` Roman Gushchin
2024-05-15 2:47 ` xiujianfeng
2024-05-15 2:45 ` xiujianfeng
1 sibling, 1 reply; 5+ messages in thread
From: Roman Gushchin @ 2024-05-14 15:21 UTC (permalink / raw)
To: Michal Hocko
Cc: Xiu Jianfeng, hannes, shakeel.butt, muchun.song, akpm, cgroups,
linux-mm, linux-kernel
On Tue, May 14, 2024 at 04:09:58PM +0200, Michal Hocko wrote:
> On Tue 14-05-24 13:11:06, Xiu Jianfeng wrote:
> > The event_list for memcg is only valid for v1 and not used for v2,
> > so it's unnessesary to handle event_list for v2.
>
> You are right but the code as is works just fine. The list will be
> empty. It is true that we do not need to take event_list_lock lock but
> nobody should be using this lock anyway. Also the offline callback is
> not particularly hot path. So why do we want to change the code?
+1 to that.
Plus this code will be moved to a separate function in mm/memcontrol-v1.c
and luckily can be compiled out entirely for users who don't need the
cgroup v1 support.
Thanks!
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH -next] memcg: don't handle event_list for v2 when offlining
2024-05-14 15:21 ` Roman Gushchin
@ 2024-05-15 2:47 ` xiujianfeng
0 siblings, 0 replies; 5+ messages in thread
From: xiujianfeng @ 2024-05-15 2:47 UTC (permalink / raw)
To: Roman Gushchin, Michal Hocko
Cc: hannes, shakeel.butt, muchun.song, akpm, cgroups, linux-mm,
linux-kernel
On 2024/5/14 23:21, Roman Gushchin wrote:
> On Tue, May 14, 2024 at 04:09:58PM +0200, Michal Hocko wrote:
>> On Tue 14-05-24 13:11:06, Xiu Jianfeng wrote:
>>> The event_list for memcg is only valid for v1 and not used for v2,
>>> so it's unnessesary to handle event_list for v2.
>>
>> You are right but the code as is works just fine. The list will be
>> empty. It is true that we do not need to take event_list_lock lock but
>> nobody should be using this lock anyway. Also the offline callback is
>> not particularly hot path. So why do we want to change the code?
>
> +1 to that.
>
> Plus this code will be moved to a separate function in mm/memcontrol-v1.c
> and luckily can be compiled out entirely for users who don't need the
> cgroup v1 support.
I found the patchset you mentioned, Thanks.
>
> Thanks!
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH -next] memcg: don't handle event_list for v2 when offlining
2024-05-14 14:09 ` Michal Hocko
2024-05-14 15:21 ` Roman Gushchin
@ 2024-05-15 2:45 ` xiujianfeng
1 sibling, 0 replies; 5+ messages in thread
From: xiujianfeng @ 2024-05-15 2:45 UTC (permalink / raw)
To: Michal Hocko
Cc: hannes, roman.gushchin, shakeel.butt, muchun.song, akpm, cgroups,
linux-mm, linux-kernel
On 2024/5/14 22:09, Michal Hocko wrote:
> On Tue 14-05-24 13:11:06, Xiu Jianfeng wrote:
>> The event_list for memcg is only valid for v1 and not used for v2,
>> so it's unnessesary to handle event_list for v2.
>
> You are right but the code as is works just fine. The list will be
> empty. It is true that we do not need to take event_list_lock lock but
> nobody should be using this lock anyway. Also the offline callback is
> not particularly hot path. So why do we want to change the code?
>
Actually, I don’t quite agree, but I don't insist on this patch.
Thanks for your feedback.
>>
>> Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
>> ---
>> mm/memcontrol.c | 12 +++++++-----
>> 1 file changed, 7 insertions(+), 5 deletions(-)
>>
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index d127c9c5fabf..4254f9cd05f4 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -5881,12 +5881,14 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
>> * Notify userspace about cgroup removing only after rmdir of cgroup
>> * directory to avoid race between userspace and kernelspace.
>> */
>> - spin_lock_irq(&memcg->event_list_lock);
>> - list_for_each_entry_safe(event, tmp, &memcg->event_list, list) {
>> - list_del_init(&event->list);
>> - schedule_work(&event->remove);
>> + if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
>> + spin_lock_irq(&memcg->event_list_lock);
>> + list_for_each_entry_safe(event, tmp, &memcg->event_list, list) {
>> + list_del_init(&event->list);
>> + schedule_work(&event->remove);
>> + }
>> + spin_unlock_irq(&memcg->event_list_lock);
>> }
>> - spin_unlock_irq(&memcg->event_list_lock);
>>
>> page_counter_set_min(&memcg->memory, 0);
>> page_counter_set_low(&memcg->memory, 0);
>> --
>> 2.34.1
>
^ permalink raw reply [flat|nested] 5+ messages in thread
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2024-05-14 13:11 [PATCH -next] memcg: don't handle event_list for v2 when offlining Xiu Jianfeng
2024-05-14 14:09 ` Michal Hocko
2024-05-14 15:21 ` Roman Gushchin
2024-05-15 2:47 ` xiujianfeng
2024-05-15 2:45 ` xiujianfeng
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