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[2003:d8:2f38:2400:62f4:c5fa:ba13:ac32]) by smtp.gmail.com with ESMTPSA id m14sm4262344wmi.39.2021.04.28.07.55.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 28 Apr 2021 07:55:00 -0700 (PDT) Subject: Re: [RFC PATCH] mm/page_alloc: fix counting of free pages after take off from buddy To: Ding Hui , akpm@linux-foundation.org, naoya.horiguchi@nec.com, osalvador@suse.de Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20210421020426.5914-1-dinghui@sangfor.com.cn> From: David Hildenbrand Organization: Red Hat Message-ID: Date: Wed, 28 Apr 2021 16:54:59 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210421020426.5914-1-dinghui@sangfor.com.cn> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21.04.21 04:04, 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. > After take_page_off_buddy, the page is no longer belong to buddy > allocator, and will not be used any more, but we maybe missed accounting > NR_FREE_PAGES in this situation. > > Signed-off-by: Ding Hui > --- > mm/page_alloc.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index cfc72873961d..8d65b62784d8 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_page_state(zone, NR_FREE_PAGES, -1); > ret = true; > break; > } > Should this use __mod_zone_freepage_state() instead? -- Thanks, David / dhildenb