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From: "HORIGUCHI NAOYA(堀口 直也)" <naoya.horiguchi@nec.com>
To: Ding Hui <dinghui@sangfor.com.cn>
Cc: "david@redhat.com" <david@redhat.com>,
	"osalvador@suse.de" <osalvador@suse.de>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: [PATCH v2] mm/page_alloc: fix counting of free pages after take off from buddy
Date: Tue, 25 May 2021 08:32:28 +0000	[thread overview]
Message-ID: <20210525083228.GA3327407@hori.linux.bs1.fc.nec.co.jp> (raw)
In-Reply-To: <20210508035533.23222-1-dinghui@sangfor.com.cn>

On Sat, May 08, 2021 at 11:55:33AM +0800, Ding Hui wrote:
> Recently we found there is a lot MemFree left in /proc/meminfo after
> do a lot of pages soft offline.
> 
> I think it's incorrect since NR_FREE_PAGES should not contain HWPoison pages.
> For offline free pages, after a successful call take_page_off_buddy(), the
> page is no longer belong to buddy allocator, and will not be used any more,
> but we missed accounting NR_FREE_PAGES in this situation.
> 
> Do update like rmqueue() does.
> 
> Signed-off-by: Ding Hui <dinghui@sangfor.com.cn>
> ---
> V2:
> use __mod_zone_freepage_state instead of __mod_zone_page_state
> 
>  mm/page_alloc.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index cfc72873961d..e124a615303b 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8947,6 +8947,7 @@ bool take_page_off_buddy(struct page *page)
>  			del_page_from_free_list(page_head, zone, page_order);
>  			break_down_buddy_pages(zone, page_head, page, 0,
>  						page_order, migratetype);
> +			__mod_zone_freepage_state(zone, -1, migratetype);

Page offline code (see set_migratetype_isolate()) seems to handle
NR_FREE_PAGES counter in its own way, so I think that it's more correct to
call __mod_zone_freepage_state() only when is_migrate_isolate(migratetype))
is false.

Otherwise, the patch looks good to me.

Thanks,
Naoya Horiguchi

>  			ret = true;
>  			break;
>  		}
> -- 
> 2.17.1
> 

  reply	other threads:[~2021-05-25  8:32 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-21  2:04 [RFC PATCH] " Ding Hui
2021-04-28 14:54 ` David Hildenbrand
2021-04-30  9:43   ` Ding Hui
2021-05-08  3:55     ` [PATCH v2] " Ding Hui
2021-05-25  8:32       ` HORIGUCHI NAOYA(堀口 直也) [this message]
2021-05-26  0:43         ` Ding Hui
2021-05-06  2:49   ` [RFC PATCH] " HORIGUCHI NAOYA(堀口 直也)
2021-05-06  4:01     ` Ding Hui
2021-05-06  7:30       ` HORIGUCHI NAOYA(堀口 直也)
2021-05-07  1:46         ` Ding Hui

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