From: Oscar Salvador <osalvador@suse.de>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-hyperv@vger.kernel.org, xen-devel@lists.xenproject.org,
linux-acpi@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Alexander Duyck <alexander.h.duyck@linux.intel.com>,
Mel Gorman <mgorman@techsingularity.net>,
Michal Hocko <mhocko@kernel.org>,
Dave Hansen <dave.hansen@intel.com>,
Vlastimil Babka <vbabka@suse.cz>,
Wei Yang <richard.weiyang@linux.alibaba.com>,
Mike Rapoport <rppt@kernel.org>,
"K. Y. Srinivasan" <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
Wei Liu <wei.liu@kernel.org>
Subject: Re: [PATCH RFC 4/4] mm/page_alloc: place pages to tail in __free_pages_core()
Date: Mon, 28 Sep 2020 09:58:24 +0200 [thread overview]
Message-ID: <20200928075820.GA4082@linux> (raw)
In-Reply-To: <20200916183411.64756-5-david@redhat.com>
On Wed, Sep 16, 2020 at 08:34:11PM +0200, David Hildenbrand wrote:
> @@ -1523,7 +1524,13 @@ void __free_pages_core(struct page *page, unsigned int order)
>
> atomic_long_add(nr_pages, &page_zone(page)->managed_pages);
> set_page_refcounted(page);
> - __free_pages(page, order);
> +
> + /*
> + * Bypass PCP and place fresh pages right to the tail, primarily
> + * relevant for memory onlining.
> + */
> + page_ref_dec(page);
> + __free_pages_ok(page, order, FOP_TO_TAIL);
Sorry, I must be missing something obvious here, but I am a bit confused here.
I get the part of placing them at the tail so rmqueue_bulk() won't
find them, but I do not get why we decrement page's refcount.
IIUC, its refcount will be 0, but why do we want to do that?
Another thing a bit unrelated... we mess three times with page's refcount
(two before this patch).
Why do we have this dance in place?
Thanks
--
Oscar Salvador
SUSE L3
next prev parent reply other threads:[~2020-09-28 7:58 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-16 18:34 [PATCH RFC 0/4] mm: place pages to the freelist tail when onling and undoing isolation David Hildenbrand
2020-09-16 18:34 ` [PATCH RFC 1/4] mm/page_alloc: convert "report" flag of __free_one_page() to a proper flag David Hildenbrand
2020-09-16 21:44 ` Alexander Duyck
2020-09-18 1:53 ` Wei Yang
2020-09-18 7:23 ` David Hildenbrand
2020-09-24 10:19 ` Vlastimil Babka
2020-09-25 10:34 ` Oscar Salvador
2020-09-16 18:34 ` [PATCH RFC 2/4] mm/page_alloc: place pages to tail in __putback_isolated_page() David Hildenbrand
2020-09-16 21:50 ` Alexander Duyck
2020-09-18 2:07 ` Wei Yang
2020-09-18 7:27 ` David Hildenbrand
2020-09-21 1:57 ` Wei Yang
2020-09-18 2:16 ` Wei Yang
2020-09-18 7:29 ` David Hildenbrand
2020-09-24 10:37 ` Vlastimil Babka
2020-09-25 8:10 ` David Hildenbrand
2020-09-25 13:19 ` Oscar Salvador
2020-09-25 13:30 ` David Hildenbrand
2020-09-16 18:34 ` [PATCH RFC 3/4] mm/page_alloc: always move pages to the tail of the freelist in unset_migratetype_isolate() David Hildenbrand
2020-09-18 2:29 ` Wei Yang
2020-09-18 7:30 ` David Hildenbrand
2020-09-24 11:13 ` Vlastimil Babka
2020-09-25 2:45 ` Wei Yang
2020-09-25 8:05 ` David Hildenbrand
2020-09-25 8:39 ` Vlastimil Babka
2020-09-25 13:13 ` David Hildenbrand
2020-09-25 13:57 ` Oscar Salvador
2020-09-16 18:34 ` [PATCH RFC 4/4] mm/page_alloc: place pages to tail in __free_pages_core() David Hildenbrand
2020-09-24 13:44 ` Vlastimil Babka
2020-09-28 7:58 ` Oscar Salvador [this message]
2020-09-28 8:36 ` David Hildenbrand
2020-09-28 12:53 ` Oscar Salvador
2020-09-16 18:50 ` [PATCH RFC 0/4] mm: place pages to the freelist tail when onling and undoing isolation osalvador
2020-09-16 19:31 ` David Hildenbrand
2020-09-18 2:30 ` Wei Yang
2020-09-18 7:32 ` David Hildenbrand
2020-09-23 14:31 ` Vlastimil Babka
2020-09-23 15:26 ` David Hildenbrand
2020-09-24 9:40 ` Mel Gorman
2020-09-24 9:54 ` David Hildenbrand
2020-09-24 13:59 ` Vlastimil Babka
2020-09-24 14:29 ` David Hildenbrand
2020-09-24 1:57 ` Wei Yang
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