From: Michal Hocko <mhocko@kernel.org>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Arun KS <arunks@codeaurora.org>,
Andrew Morton <akpm@linux-foundation.org>,
Oscar Salvador <osalvador@suse.de>,
Pavel Tatashin <pasha.tatashin@soleen.com>,
Dan Williams <dan.j.williams@intel.com>
Subject: Re: [PATCH v1 2/4] mm/memory_hotplug: Handle unaligned start and nr_pages in online_pages_blocks()
Date: Wed, 14 Aug 2019 18:02:20 +0200 [thread overview]
Message-ID: <20190814160220.GF17933@dhcp22.suse.cz> (raw)
In-Reply-To: <8d1ba12d-9993-1822-38e4-422a46108fec@redhat.com>
On Wed 14-08-19 16:28:21, David Hildenbrand wrote:
> On 14.08.19 16:17, David Hildenbrand wrote:
> > On 14.08.19 16:08, Michal Hocko wrote:
> >> On Fri 09-08-19 14:56:59, David Hildenbrand wrote:
> >>> Take care of nr_pages not being a power of two and start not being
> >>> properly aligned. Essentially, what walk_system_ram_range() could provide
> >>> to us. get_order() will round-up in case it's not a power of two.
> >>>
> >>> This should only apply to memory blocks that contain strange memory
> >>> resources (especially with holes), not to ordinary DIMMs.
> >>
> >> I would really like to see an example of such setup before making the
> >> code hard to read. Because I am not really sure something like that
> >> exists at all.
> >
> > I don't have a real-live example at hand (founds this while exploring
> > the code), however, the linked commit changed it without stating why it
> > would be safe to do so.
>
> So, while I agree that "not a power of two" is rare, are you sure we
> will only have holes that are aligned to 4MB (especially on x86)?
No I am not saying that because I do not know. I am not aware of any
such HW but that doesn't really mean anything. But I would like to see
an example and have it archived in the changelog before we make the code
more complicated.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-08-14 16:02 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-09 12:56 [PATCH v1 0/4] mm/memory_hotplug: online_pages() cleanups David Hildenbrand
2019-08-09 12:56 ` [PATCH v1 1/4] resource: Use PFN_UP / PFN_DOWN in walk_system_ram_range() David Hildenbrand
2019-08-14 14:06 ` Michal Hocko
2019-08-09 12:56 ` [PATCH v1 2/4] mm/memory_hotplug: Handle unaligned start and nr_pages in online_pages_blocks() David Hildenbrand
2019-08-09 21:46 ` Andrew Morton
2019-08-10 9:18 ` David Hildenbrand
2019-08-14 14:08 ` Michal Hocko
2019-08-14 14:17 ` David Hildenbrand
2019-08-14 14:28 ` David Hildenbrand
2019-08-14 16:02 ` Michal Hocko [this message]
2019-08-14 14:28 ` Michal Hocko
2019-08-09 12:57 ` [PATCH v1 3/4] mm/memory_hotplug: Simplify online_pages_range() David Hildenbrand
2019-08-14 14:19 ` Michal Hocko
2019-08-14 14:23 ` David Hildenbrand
2019-08-09 12:57 ` [PATCH v1 4/4] mm/memory_hotplug: online_pages cannot be 0 in online_pages() David Hildenbrand
2019-08-14 14:26 ` Michal Hocko
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