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From: Michal Hocko <mhocko@kernel.org>
To: Oscar Salvador <osalvador@suse.de>
Cc: Qian Cai <cai@lca.pw>,
	akpm@linux-foundation.org, vbabka@suse.cz, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] mm/hotplug: fix offline undo_isolate_page_range()
Date: Thu, 14 Mar 2019 09:22:19 +0100
Message-ID: <20190314082219.GD7473@dhcp22.suse.cz> (raw)
In-Reply-To: <20190314080922.dk5ljg7fbtarzrog@d104.suse.de>

On Thu 14-03-19 09:09:22, Oscar Salvador wrote:
> On Wed, Mar 13, 2019 at 10:31:33AM -0400, Qian Cai wrote:
> > Also, after calling the "useless" undo_isolate_page_range() here, it
> > reaches the point of no returning by notifying MEM_OFFLINE. Those pages
> > will be marked as MIGRATE_MOVABLE again once onlining. The only thing
> > left to do is to decrease the number of isolated pageblocks zone
> > counter which would make some paths of the page allocation slower that
> > the above commit introduced. A memory block is usually at most 1GiB in
> > size, so an "int" should be enough to represent the number of pageblocks
> > in a block. Fix an incorrect comment along the way.
> 
> Well, x86_64's memblocks can be up to 2GB depending on the memory we got.
> Plus the fact that alloc_contig_range can be used to isolate 16GB-hugetlb
> pages on powerpc, and that could be a lot of pageblocks.
> 
> While an "int" could still hold, I think we should use "long" just to be
> more future-proof.

I would rather not touch that for now. If we really need to change the
type then do it when it is really needed. I pressume more things would
have to be changed anyway.

-- 
Michal Hocko
SUSE Labs


  reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-13 14:31 Qian Cai
2019-03-14  8:05 ` Michal Hocko
2019-03-14  8:09 ` Oscar Salvador
2019-03-14  8:22   ` Michal Hocko [this message]
2019-03-14  8:10 ` Oscar Salvador

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