From: Michal Hocko <mhocko@kernel.org>
To: Rashmica Gupta <rashmica.g@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>,
David Hildenbrand <david@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Dan Williams <dan.j.williams@intel.com>,
pasha.tatashin@soleen.com, Jonathan.Cameron@huawei.com,
anshuman.khandual@arm.com, Vlastimil Babka <vbabka@suse.cz>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 0/5] Allocate memmap from hotadded memory
Date: Thu, 1 Aug 2019 09:17:09 +0200 [thread overview]
Message-ID: <20190801071709.GE11627@dhcp22.suse.cz> (raw)
In-Reply-To: <4ddee0dd719abd50350f997b8089fa26f6004c0c.camel@gmail.com>
On Thu 01-08-19 09:06:40, Rashmica Gupta wrote:
> On Wed, 2019-07-31 at 14:08 +0200, Michal Hocko wrote:
> > On Tue 02-07-19 18:52:01, Rashmica Gupta wrote:
> > [...]
> > > > 2) Why it was designed, what is the goal of the interface?
> > > > 3) When it is supposed to be used?
> > > >
> > > >
> > > There is a hardware debugging facility (htm) on some power chips.
> > > To use
> > > this you need a contiguous portion of memory for the output to be
> > > dumped
> > > to - and we obviously don't want this memory to be simultaneously
> > > used by
> > > the kernel.
> >
> > How much memory are we talking about here? Just curious.
>
> From what I've seen a couple of GB per node, so maybe 2-10GB total.
OK, that is really a lot to keep around unused just in case the
debugging is going to be used.
I am still not sure the current approach of (ab)using memory hotplug is
ideal. Sure there is some overlap but you shouldn't really need to
offline the required memory range at all. All you need is to isolate the
memory from any existing user and the page allocator. Have you checked
alloc_contig_range?
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-08-01 7:17 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-25 7:52 [PATCH v2 0/5] Allocate memmap from hotadded memory Oscar Salvador
2019-06-25 7:52 ` [PATCH v2 1/5] drivers/base/memory: Remove unneeded check in remove_memory_block_devices Oscar Salvador
2019-06-25 8:01 ` David Hildenbrand
2019-06-25 8:03 ` David Hildenbrand
2019-06-25 8:09 ` Oscar Salvador
2019-06-25 8:27 ` David Hildenbrand
2019-06-25 7:52 ` [PATCH v2 2/5] mm,memory_hotplug: Introduce MHP_VMEMMAP_FLAGS Oscar Salvador
2019-06-25 8:31 ` David Hildenbrand
2019-07-24 20:11 ` Dan Williams
2019-07-24 21:36 ` osalvador
2019-07-25 9:27 ` Oscar Salvador
2019-07-25 9:30 ` David Hildenbrand
2019-07-25 9:40 ` Oscar Salvador
2019-07-25 10:04 ` David Hildenbrand
2019-07-25 10:13 ` Oscar Salvador
2019-07-25 10:15 ` David Hildenbrand
2019-06-25 7:52 ` [PATCH v2 3/5] mm,memory_hotplug: Introduce Vmemmap page helpers Oscar Salvador
2019-06-25 10:28 ` David Hildenbrand
2019-06-26 9:48 ` Oscar Salvador
2019-06-25 7:52 ` [PATCH v2 4/5] mm,memory_hotplug: allocate memmap from the added memory range for sparse-vmemmap Oscar Salvador
2019-06-25 8:49 ` David Hildenbrand
2019-06-26 8:13 ` Oscar Salvador
2019-06-26 8:15 ` David Hildenbrand
2019-06-26 8:17 ` Anshuman Khandual
2019-06-26 8:28 ` Oscar Salvador
2019-07-24 21:49 ` Dan Williams
2019-06-25 7:52 ` [PATCH v2 5/5] mm,memory_hotplug: Allow userspace to enable/disable vmemmap Oscar Salvador
2019-06-25 8:25 ` [PATCH v2 0/5] Allocate memmap from hotadded memory David Hildenbrand
2019-06-25 8:33 ` David Hildenbrand
2019-06-26 8:03 ` Oscar Salvador
2019-06-26 8:11 ` David Hildenbrand
2019-06-26 8:15 ` Oscar Salvador
2019-06-26 8:27 ` Oscar Salvador
2019-06-26 8:37 ` David Hildenbrand
2019-06-26 8:28 ` David Hildenbrand
2019-07-02 6:42 ` Rashmica Gupta
2019-07-02 7:48 ` Oscar Salvador
2019-07-02 8:52 ` Rashmica Gupta
2019-07-10 1:14 ` Rashmica Gupta
2019-07-31 12:08 ` Michal Hocko
2019-07-31 23:06 ` Rashmica Gupta
2019-08-01 7:17 ` Michal Hocko [this message]
2019-08-01 7:18 ` David Hildenbrand
2019-08-01 7:24 ` Michal Hocko
2019-08-01 7:26 ` David Hildenbrand
2019-08-01 7:31 ` David Hildenbrand
2019-08-01 7:39 ` Michal Hocko
2019-08-01 7:48 ` Michal Hocko
2019-08-01 9:18 ` David Hildenbrand
2019-08-01 7:34 ` Michal Hocko
2019-08-01 7:50 ` David Hildenbrand
2019-08-01 8:04 ` Michal Hocko
2019-07-16 12:28 ` David Hildenbrand
2019-07-29 5:42 ` Rashmica Gupta
2019-07-29 8:06 ` David Hildenbrand
2019-07-30 7:08 ` Rashmica Gupta
2019-07-31 2:21 ` Rashmica Gupta
2019-07-31 9:39 ` David Hildenbrand
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