linux-kernel - Re: [PATCH 7/9] memcg: use __mod_memcg_state in drain_obj

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Message-ID: <ca8ed915-28b2-48a0-9d8e-dbdcf15b94d6@suse.cz>
Date: Tue, 18 Mar 2025 08:50:10 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Roman Gushchin <roman.gushchin@...ux.dev>,
 Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>,
 Muchun Song <muchun.song@...ux.dev>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>, linux-mm@...ck.org,
 cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
 Meta kernel team <kernel-team@...a.com>
Subject: Re: [PATCH 7/9] memcg: use __mod_memcg_state in drain_obj_stock

On 3/18/25 02:13, Roman Gushchin wrote:
> On Sat, Mar 15, 2025 at 10:49:28AM -0700, Shakeel Butt wrote:
>> For non-PREEMPT_RT kernels, drain_obj_stock() is always called with irq
>> disabled, so we can use __mod_memcg_state() instead of
>> mod_memcg_state(). For PREEMPT_RT, we need to add memcg_stats_[un]lock
>> in __mod_memcg_state().
>> 
>> Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>
>> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
>> ---
>>  mm/memcontrol.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>> 
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index 3c4de384b5a0..dfe9c2eb7816 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -707,10 +707,12 @@ void __mod_memcg_state(struct mem_cgroup *memcg, enum memcg_stat_item idx,
>>  	if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx))
>>  		return;
>>  
>> +	memcg_stats_lock();
>>  	__this_cpu_add(memcg->vmstats_percpu->state[i], val);
>>  	val = memcg_state_val_in_pages(idx, val);
>>  	memcg_rstat_updated(memcg, val);
>>  	trace_mod_memcg_state(memcg, idx, val);
>> +	memcg_stats_unlock();
>>  }
>>  
>>  #ifdef CONFIG_MEMCG_V1
>> @@ -2845,7 +2847,7 @@ static void drain_obj_stock(struct memcg_stock_pcp *stock)
> 
> VM_WARN_ON_IRQS_ENABLED() ?

It's part of memcg_stats_lock()

> Reviewed-by: Roman Gushchin <roman.gushchin@...ux.dev>