linux-kernel - Re: [PATCH v1 6/9] mm: memcg: put memcg1-specific struct mem_cgroup's members under CONFIG_MEMCG

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Date: Fri, 28 Jun 2024 17:48:54 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Roman Gushchin <roman.gushchin@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, Johannes Weiner <hannes@...xchg.org>, 
	Michal Hocko <mhocko@...nel.org>, Muchun Song <muchun.song@...ux.dev>
Subject: Re: [PATCH v1 6/9] mm: memcg: put memcg1-specific struct
 mem_cgroup's members under CONFIG_MEMCG_V1

On Fri, Jun 28, 2024 at 09:03:14PM GMT, Roman Gushchin wrote:
> Put memcg1-specific members of struct mem_cgroup under the
> CONFIG_MEMCG_V1 config option. Also group them close to the end
> of struct mem_cgroup just before the dynamic per-node part.
> 
> Signed-off-by: Roman Gushchin <roman.gushchin@...ux.dev>
> ---
>  include/linux/memcontrol.h | 103 +++++++++++++++++++------------------
>  1 file changed, 53 insertions(+), 50 deletions(-)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 44ab6394c9ed..107b0c5d6eab 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -188,10 +188,6 @@ struct mem_cgroup {
>  		struct page_counter memsw;	/* v1 only */
>  	};
>  
> -	/* Legacy consumer-oriented counters */
> -	struct page_counter kmem;		/* v1 only */
> -	struct page_counter tcpmem;		/* v1 only */
> -
>  	/* Range enforcement for interrupt charges */
>  	struct work_struct high_work;
>  
> @@ -205,8 +201,6 @@ struct mem_cgroup {
>  	bool zswap_writeback;
>  #endif
>  
> -	unsigned long soft_limit;
> -
>  	/* vmpressure notifications */
>  	struct vmpressure vmpressure;
>  
> @@ -215,13 +209,7 @@ struct mem_cgroup {
>  	 */
>  	bool oom_group;
>  
> -	/* protected by memcg_oom_lock */
> -	bool		oom_lock;
> -	int		under_oom;
> -
> -	int	swappiness;
> -	/* OOM-Killer disable */
> -	int		oom_kill_disable;
> +	int swappiness;
>  
>  	/* memory.events and memory.events.local */
>  	struct cgroup_file events_file;
> @@ -230,27 +218,6 @@ struct mem_cgroup {
>  	/* handle for "memory.swap.events" */
>  	struct cgroup_file swap_events_file;
>  
> -	/* protect arrays of thresholds */
> -	struct mutex thresholds_lock;
> -
> -	/* thresholds for memory usage. RCU-protected */
> -	struct mem_cgroup_thresholds thresholds;
> -
> -	/* thresholds for mem+swap usage. RCU-protected */
> -	struct mem_cgroup_thresholds memsw_thresholds;
> -
> -	/* For oom notifier event fd */
> -	struct list_head oom_notify;
> -
> -	/*
> -	 * Should we move charges of a task when a task is moved into this
> -	 * mem_cgroup ? And what type of charges should we move ?
> -	 */
> -	unsigned long move_charge_at_immigrate;
> -	/* taken only while moving_account > 0 */
> -	spinlock_t		move_lock;
> -	unsigned long		move_lock_flags;
> -
>  	CACHELINE_PADDING(_pad1_);

Let's also remove these _pad1_ and also _pad2_ as well as this
rearrangement nullifies the reasons behind these paddings. We need to
run some perf benchmarks to identify the newer false cache sharing
ields.