linux-kernel - Re: [PATCH RFC v4 11/13] mm/vmscan: Move count_vm_event(DROP_SLAB) into drop

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Date:   Tue, 25 Feb 2020 15:13:39 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        virtio-dev@...ts.oasis-open.org,
        virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH RFC v4 11/13] mm/vmscan: Move count_vm_event(DROP_SLAB)
 into drop_slab()

On Thu 12-12-19 18:11:35, David Hildenbrand wrote:
> Let's count within the function itself, so every invocation (of future
> users) will be counted.
> 
> Cc: Alexander Viro <viro@...iv.linux.org.uk>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: linux-fsdevel@...r.kernel.org
> Signed-off-by: David Hildenbrand <david@...hat.com>

Slight inconsistency with the page cache droppint but nothing earth
shattering.

Acked-by: Michal Hocko <mhocko@...e.com>

> ---
>  fs/drop_caches.c | 4 +---
>  mm/vmscan.c      | 1 +
>  2 files changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/drop_caches.c b/fs/drop_caches.c
> index d31b6c72b476..a042da782fcd 100644
> --- a/fs/drop_caches.c
> +++ b/fs/drop_caches.c
> @@ -61,10 +61,8 @@ int drop_caches_sysctl_handler(struct ctl_table *table, int write,
>  			iterate_supers(drop_pagecache_sb, NULL);
>  			count_vm_event(DROP_PAGECACHE);
>  		}
> -		if (sysctl_drop_caches & 2) {
> +		if (sysctl_drop_caches & 2)
>  			drop_slab();
> -			count_vm_event(DROP_SLAB);
> -		}
>  		if (!stfu) {
>  			pr_info("%s (%d): drop_caches: %d\n",
>  				current->comm, task_pid_nr(current),
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 5a6445e86328..c3e53502a84a 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -726,6 +726,7 @@ void drop_slab(void)
>  
>  	for_each_online_node(nid)
>  		drop_slab_node(nid);
> +	count_vm_event(DROP_SLAB);
>  }
>  
>  static inline int is_page_cache_freeable(struct page *page)
> -- 
> 2.23.0

-- 
Michal Hocko
SUSE Labs