From: Michal Hocko <mhocko@kernel.org>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Pavel Tatashin <pasha.tatashin@soleen.com>,
Dan Williams <dan.j.williams@intel.com>,
Oscar Salvador <osalvador@suse.de>
Subject: Re: [PATCH v1] drivers/base/memory.c: Don't store end_section_nr in memory blocks
Date: Wed, 31 Jul 2019 16:37:14 +0200 [thread overview]
Message-ID: <20190731143714.GX9330@dhcp22.suse.cz> (raw)
In-Reply-To: <c92a4d6f-b0f2-e080-5157-b90ab61a8c49@redhat.com>
On Wed 31-07-19 16:21:46, David Hildenbrand wrote:
[...]
> > Thinking about it some more, I believe that we can reasonably provide
> > both APIs controlable by a command line parameter for backwards
> > compatibility. It is the hotplug code to control sysfs APIs. E.g.
> > create one sysfs entry per add_memory_resource for the new semantic.
>
> Yeah, but the real question is: who needs it. I can only think about
> some DIMM scenarios (some, not all). I would be interested in more use
> cases. Of course, to provide and maintain two APIs we need a good reason.
Well, my 3TB machine that has 7 movable nodes could really go with less
than
$ find /sys/devices/system/memory -name "memory*" | wc -l
1729
when it doesn't really make any sense to offline less than a
hotremovable entity which is the whole node effectivelly. I have seen
reports where a similarly large machine chocked on boot just because of
too many udev events...
In other words allowing smaller granularity is a nice toy but real
usecases usually work with the whole hotplugable entity (e.g. the whole
ACPI container).
> (one sysfs per add_memory_resource() won't cover all DIMMs completely as
> far as I remember - I might be wrong, I remember there could be a
> sequence of add_memory(). Also, some DIMMs might actually overlap with
> memory indicated during boot - complicated stuff)
Which is something we have to live with anyway due to nodes interleaving.
So nothing really new.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-07-31 14:37 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-31 12:22 [PATCH v1] drivers/base/memory.c: Don't store end_section_nr in memory blocks David Hildenbrand
2019-07-31 12:43 ` Michal Hocko
2019-07-31 13:12 ` David Hildenbrand
2019-07-31 13:25 ` Michal Hocko
2019-07-31 13:42 ` David Hildenbrand
2019-07-31 14:04 ` David Hildenbrand
2019-07-31 14:15 ` Michal Hocko
2019-07-31 14:23 ` David Hildenbrand
2019-07-31 14:14 ` Michal Hocko
2019-07-31 14:21 ` David Hildenbrand
2019-07-31 14:37 ` Michal Hocko [this message]
2019-07-31 14:43 ` David Hildenbrand
2019-08-01 6:13 ` Michal Hocko
2019-08-01 7:00 ` David Hildenbrand
2019-08-01 8:27 ` Michal Hocko
2019-08-01 8:36 ` David Hildenbrand
2019-07-31 20:57 ` Andrew Morton
2019-08-01 6:48 ` David Hildenbrand
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