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From: Michal Hocko <mhocko@kernel.org>
To: Igor Stoppa <igor.stoppa@huawei.com>
Cc: Joonsoo Kim <js1304@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Rik van Riel <riel@redhat.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	mgorman@techsingularity.net, Laura Abbott <lauraa@codeaurora.org>,
	Minchan Kim <minchan@kernel.org>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Michal Nazarewicz <mina86@mina86.com>,
	"Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	Russell King <linux@armlinux.org.uk>,
	Will Deacon <will.deacon@arm.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	kernel-team@lge.com
Subject: Re: Generic approach to customizable zones - was: Re: [PATCH v7 0/7] Introduce ZONE_CMA
Date: Fri, 28 Apr 2017 10:36:28 +0200	[thread overview]
Message-ID: <20170428083625.GG8143@dhcp22.suse.cz> (raw)
In-Reply-To: <d3c0d01c-ef3f-56f8-2701-a32f8be2d13b@huawei.com>

I didn't read this thoughly yet because I will be travelling shortly but
this point alone just made ask, because it seems there is some
misunderstanding

On Fri 28-04-17 11:04:27, Igor Stoppa wrote:
[...]
> * if one is happy to have a 64bits type, allow for as many zones as
>   it's possible to fit, or anyway more than what is possible with
>   the 32 bit mask.

zones are currently placed in struct page::flags. And that already is
64b size on 64b arches. And we do not really have any room spare there.
We encode page flags, zone id, numa_nid/sparse section_nr there. How can
you add more without enlarging the struct page itself or using external
means to store the same information (page_ext comes to mind)? Even if
the later would be possible then note thatpage_zone() is used in many
performance sensitive paths and making it perform well with special
casing would be far from trivial.
-- 
Michal Hocko
SUSE Labs

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  reply	other threads:[~2017-04-28  8:36 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-11  3:17 js1304
2017-04-11  3:17 ` [PATCH v7 1/7] mm/page_alloc: don't reserve ZONE_HIGHMEM for ZONE_MOVABLE request js1304
2017-04-17  7:38   ` Minchan Kim
2017-04-21  1:32     ` Joonsoo Kim
2017-04-11  3:17 ` [PATCH v7 2/7] mm/cma: introduce new zone, ZONE_CMA js1304
2017-04-11  3:17 ` [PATCH v7 3/7] mm/cma: populate ZONE_CMA js1304
2017-04-11  3:17 ` [PATCH v7 4/7] mm/cma: remove ALLOC_CMA js1304
2017-04-11  3:17 ` [PATCH v7 5/7] mm/cma: remove MIGRATE_CMA js1304
2017-04-11  3:17 ` [PATCH v7 6/7] mm/cma: remove per zone CMA stat js1304
2017-04-11  3:17 ` [PATCH v7 7/7] ARM: CMA: avoid re-mapping CMA region if CONFIG_HIGHMEM js1304
2017-04-11 18:15 ` [PATCH v7 0/7] Introduce ZONE_CMA Michal Hocko
2017-04-12  1:35   ` Joonsoo Kim
2017-04-13 11:56     ` Michal Hocko
2017-04-17  2:02       ` Joonsoo Kim
2017-04-21  1:35         ` Joonsoo Kim
2017-04-21  6:54           ` Michal Hocko
2017-04-24 13:09         ` Michal Hocko
2017-04-25  3:42           ` Joonsoo Kim
2017-04-27 15:06             ` Michal Hocko
2017-04-28  8:04               ` Generic approach to customizable zones - was: " Igor Stoppa
2017-04-28  8:36                 ` Michal Hocko [this message]
2017-04-28  9:04                   ` Igor Stoppa
2017-05-02  4:01               ` Joonsoo Kim
2017-05-02 13:32                 ` Michal Hocko
2017-05-11  2:12                   ` Joonsoo Kim
2017-05-11  9:13                     ` Michal Hocko
2017-05-12  2:00                       ` Joonsoo Kim
2017-05-12  6:38                         ` Michal Hocko
2017-05-15  3:57                           ` Joonsoo Kim
2017-05-16  8:47                             ` Michal Hocko
2017-05-17  7:44                               ` Joonsoo Kim
2017-05-02  8:06               ` Vlastimil Babka
2017-05-02 13:03                 ` Michal Hocko
2017-05-02 13:41                   ` Igor Stoppa
2017-05-04 12:33                   ` Vlastimil Babka
2017-05-04 12:46                     ` Michal Hocko
2017-05-11  8:51                       ` Vlastimil Babka
2017-04-12  1:39 ` Joonsoo Kim
2017-04-24  4:08 ` Bob Liu

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