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Date: Mon, 2 Jun 2025 07:01:26 +0200
From: Christoph Hellwig <hch@lst.de>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	David Hildenbrand <david@redhat.com>, lorenzo.stoakes@oracle.com,
	Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org,
	surenb@google.com, mhocko@suse.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org,
	Hongyu Ning <hongyu.ning@linux.intel.com>, stable@vger.kernel.org,
	Christoph Hellwig <hch@lst.de>, Hannes Reinecke <hare@suse.de>,
	Johannes Thumshirn <johannes.thumshirn@wdc.com>,
	Jens Axboe <axboe@kernel.dk>
Subject: Re: [PATCH] mm: Fix vmstat after removing NR_BOUNCE
Message-ID: <20250602050126.GB21716@lst.de>
References: <20250529103832.2937460-1-kirill.shutemov@linux.intel.com>
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In-Reply-To: <20250529103832.2937460-1-kirill.shutemov@linux.intel.com>
User-Agent: Mutt/1.5.17 (2007-11-01)

On Thu, May 29, 2025 at 01:38:32PM +0300, Kirill A. Shutemov wrote:
> Hongyu noticed that the nr_unaccepted counter kept growing even in the
> absence of unaccepted memory on the machine.
> 
> This happens due to a commit that removed NR_BOUNCE: it removed the
> counter from the enum zone_stat_item, but left it in the vmstat_text
> array.
> 
> As a result, all counters below nr_bounce in /proc/vmstat are
> shifted by one line, causing the numa_hit counter to be labeled as
> nr_unaccepted.
> 
> To fix this issue, remove nr_bounce from the vmstat_text array.

Ooops, yes:

Reviewed-by: Christoph Hellwig <hch@lst.de>

> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 4c268ce39ff2..ae9882063d89 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -1201,7 +1201,6 @@ const char * const vmstat_text[] = {
>  	"nr_zone_unevictable",
>  	"nr_zone_write_pending",
>  	"nr_mlock",
> -	"nr_bounce",
>  #if IS_ENABLED(CONFIG_ZSMALLOC)
>  	"nr_zspages",
>  #endif

It would be really useful if such pretty printing arrays used
named initializers, as that would make it obvious that an entry
needs removal.