From: Sharath Kumar Bhat <sharath.k.bhat@linux.intel.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Sharath Kumar Bhat <sharath.k.bhat@linux.intel.com>,
linux-mm@kvack.org, akpm@linux-foundation.org
Subject: Re: [PATCH] mm: fix movable_node kernel command-line
Date: Mon, 23 Oct 2017 09:03:14 -0700 [thread overview]
Message-ID: <20171023160314.GA11853@linux.intel.com> (raw)
In-Reply-To: <20171023125213.whdiev6bjxr72gow@dhcp22.suse.cz>
On Mon, Oct 23, 2017 at 02:52:13PM +0200, Michal Hocko wrote:
> On Fri 20-10-17 16:32:09, Sharath Kumar Bhat wrote:
> > Currently when booted with the 'movable_node' kernel command-line the user
> > can not have both the functionality of 'movable_node' and at the same time
> > specify more movable memory than the total size of hotpluggable memories.
> >
> > This is a problem because it limits the total amount of movable memory in
> > the system to the total size of hotpluggable memories and in a system the
> > total size of hotpluggable memories can be very small or all hotpluggable
> > memories could have been offlined. The 'movable_node' parameter was aimed
> > to provide the entire memory of hotpluggable NUMA nodes to applications
> > without any kernel allocations in them. The 'movable_node' option will be
> > useful if those hotpluggable nodes have special memory like MCDRAM as in
> > KNL which is a high bandwidth memory and the user would like to use all of
> > it for applications. But in doing so the 'movable_node' command-line poses
> > this limitation and does not allow the user to specify more movable memory
> > in addition to the hotpluggable memories.
> >
> > With this change the existing 'movablecore=' and 'kernelcore=' command-line
> > parameters can be specified in addition to the 'movable_node' kernel
> > parameter. This allows the user to boot the kernel with an increased amount
> > of movable memory in the system and still have only movable memory in
> > hotpluggable NUMA nodes.
>
> I really detest making the already cluttered kernelcore* handling even
> more so. Why cannot your MCDRAM simply announce itself as hotplugable?
> Also it is not really clear to me how can you control that only your
> specific memory type gets into movable zone.
> --
> Michal Hocko
> SUSE Labs
In the example MCDRAM is already being announced as hotpluggable and
'movable_node' is also used to ensure that there is no kernel allocations
in that. This is a required functionality but when done so user can not have
movable zone in other non-hotpluggable memories in addition to hotpluggable
memory.
This change wont affect any of the present use cases such as 'kernelcore='
or 'movablecore=' or using only 'movable_node'. They continue to work as
before.
In addition to those it lets admin to specify 'kernelcore=' or
'movablecore=' when using 'movable_node' command-line
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next prev parent reply other threads:[~2017-10-23 16:03 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-20 23:32 [PATCH] mm: fix movable_node kernel command-line Sharath Kumar Bhat
2017-10-23 12:52 ` Michal Hocko
2017-10-23 16:03 ` Sharath Kumar Bhat [this message]
2017-10-23 16:15 ` Michal Hocko
2017-10-23 17:14 ` Sharath Kumar Bhat
2017-10-23 17:20 ` Michal Hocko
2017-10-23 17:35 ` Sharath Kumar Bhat
2017-10-23 17:49 ` Michal Hocko
2017-10-23 18:48 ` Sharath Kumar Bhat
2017-10-23 19:04 ` Michal Hocko
2017-10-23 19:25 ` Sharath Kumar Bhat
2017-10-23 19:35 ` Michal Hocko
2017-10-23 19:56 ` Sharath Kumar Bhat
2017-10-23 21:52 ` Dave Hansen
2017-10-24 1:06 ` Sharath Kumar Bhat
2017-10-24 7:19 ` Michal Hocko
2017-10-25 0:53 ` Sharath Kumar Bhat
2017-10-25 6:38 ` Michal Hocko
2017-10-25 22:01 ` Sharath Kumar Bhat
2017-10-26 7:36 ` Michal Hocko
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