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From: Vlastimil Babka <vbabka@suse.cz>
To: Michal Hocko <mhocko@kernel.org>
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>,
	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, Heiko Carstens <heiko.carstens@de.ibm.com>,
	Martin Schwidefsky <schwidefsky@de.ibm.com>
Subject: Re: [PATCH v7 0/7] Introduce ZONE_CMA
Date: Thu, 11 May 2017 10:51:17 +0200	[thread overview]
Message-ID: <203a7f52-d444-dbcc-0cc0-0c77dffbcadd@suse.cz> (raw)
In-Reply-To: <20170504124648.GG31540@dhcp22.suse.cz>

On 05/04/2017 02:46 PM, Michal Hocko wrote:
> On Thu 04-05-17 14:33:24, Vlastimil Babka wrote:
>>>
>>> I am pretty sure s390 and ppc support NUMA and aim at supporting really
>>> large systems. 
>>
>> I don't see ppc there,
> 
> config KVM_BOOK3S_64_HV
>         tristate "KVM for POWER7 and later using hypervisor mode in host"
>         depends on KVM_BOOK3S_64 && PPC_POWERNV
>         select KVM_BOOK3S_HV_POSSIBLE
>         select MMU_NOTIFIER
>         select CMA
> 
> fa61a4e376d21 tries to explain some more

Uh, that's unfortunate then.

> [...]
>>> Are we really ready to add another thing like that? How are distribution
>>> kernels going to handle that?
>>
>> I still hope that generic enterprise/desktop distributions can disable
>> it, and it's only used for small devices with custom kernels.
>>
>> The config burden is already there in any case, it just translates to
>> extra migratetype and fastpath hooks, not extra zone and potentially
>> less nodes.
> 
> AFAIU the extra migrate type costs nothing when there are no cma
> reservations. And those hooks can be made noop behind static branch
> as well. So distribution kernels do not really have to be afraid of
> enabling CMA currently.

The tradeoff is unfortunate :/

  reply	other threads:[~2017-05-11  8:51 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-11  3:17 [PATCH v7 0/7] Introduce ZONE_CMA 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
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 [this message]
2017-04-12  1:39 ` Joonsoo Kim
2017-04-24  4:08 ` Bob Liu

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