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From: Oscar Salvador <osalvador@suse.de>
To: David Hildenbrand <david@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Pavel Tatashin <pasha.tatashin@soleen.com>,
	Michal Hocko <mhocko@suse.com>, Linux MM <linux-mm@kvack.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/2] mm,memory_hotplug: Fix shrink_{zone,node}_span
Date: Wed, 17 Jul 2019 10:08:03 +0200
Message-ID: <20190717080755.GA22661@linux> (raw)
In-Reply-To: <da07d964-fcfa-1406-bc12-faebbe38696e@redhat.com>

On Wed, Jul 17, 2019 at 10:01:01AM +0200, David Hildenbrand wrote:
> I'd also like to note that we should strive for making all zone-related
> changes when offlining in the future, not when removing memory. So
> ideally, any core changes we perform from now, should make that step
> (IOW implementing that) easier, not harder. Of course, BUGs have to be
> fixed.
> 
> The rough idea would be to also mark ZONE_DEVICE sections as ONLINE (or
> rather rename it to "ACTIVE" to generalize).
> 
> For each section we would then have
> 
> - pfn_valid(): We have a valid "struct page" / memmap
> - pfn_present(): We have actually added that memory via an oficial
>   interface to mm (e.g., arch_add_memory() )
> - pfn_online() / (or pfn_active()): Memory is active (online in "buddy"-
>   speak, or memory that was moved to the ZONE_DEVICE zone)
> 
> When resizing the zones (e.g., when offlining memory), we would then
> search for pfn_online(), not pfn_present().
> 
> In addition to move_pfn_range_to_zone(), we would have
> remove_pfn_range_from_zone(), called during offline_pages() / by
> devmem/hmm/pmem code before removing.
> 
> (I started to look into this, but I don't have any patches yet)

Yes, it seems like a good approach, and something that makes sense
to pursue.
FWIF, I sent a patchset [1] for that a long time ago, but I could not
follow-up due to time constraints.

[1] https://patchwork.kernel.org/cover/10700783/


-- 
Oscar Salvador
SUSE L3


  reply index

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-15  8:15 [PATCH 0/2] Fixes for sub-section hotplug Oscar Salvador
2019-07-15  8:15 ` [PATCH 1/2] mm,sparse: Fix deactivate_section for early sections Oscar Salvador
2019-07-15 16:02   ` Aneesh Kumar K.V
2019-07-16  4:33   ` Dan Williams
2019-07-18 12:07   ` David Hildenbrand
2019-07-15  8:15 ` [PATCH 2/2] mm,memory_hotplug: Fix shrink_{zone,node}_span Oscar Salvador
2019-07-15 16:11   ` Aneesh Kumar K.V
2019-07-15 21:24     ` Oscar Salvador
2019-07-17  2:28       ` Dan Williams
2019-07-17  7:38         ` Oscar Salvador
2019-07-17  8:01           ` David Hildenbrand
2019-07-17  8:08             ` Oscar Salvador [this message]
2019-07-17  5:38       ` Aneesh Kumar K.V
2019-07-17  7:42         ` Oscar Salvador
2019-07-18 12:05   ` Oscar Salvador

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