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From: Michal Hocko <mhocko@kernel.org>
To: "Fontenot, Nathan" <ndfont@gmail.com>
Cc: David Hildenbrand <david@redhat.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Dan Williams <dan.j.williams@intel.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	powerpc-utils-devel@googlegroups.com, util-linux@vger.kernel.org,
	Badari Pulavarty <pbadari@us.ibm.com>,
	Robert Jennings <rcj@linux.vnet.ibm.com>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	Karel Zak <kzak@redhat.com>
Subject: Re: [PATCH RFC] drivers/base/memory.c: indicate all memory blocks as removable
Date: Mon, 27 Jan 2020 10:23:34 +0100
Message-ID: <20200127092334.GB1183@dhcp22.suse.cz> (raw)
In-Reply-To: <ddb71703-81fa-53fe-51de-c018612f2704@gmail.com>

On Fri 24-01-20 13:10:22, Fontenot, Nathan wrote:
> It's been awhile since I've looked at the powerpc-utils drmgr command and
> pseries DLPAR code but a quick scan makes and it appears that it hasn't changed
> too much. Given that, some thoughts.
> The sysfs 'removable' file was a great help when memory DLPAR was driven
> from userspace in the powerpc-utils drmgr command. Having this check did improve
> performance though I can't point to any numbers.

Do you still have an access to the HW to give it a try?

> Currently, memory DLPAR is done completely in the kernel. The request is
> initiated from drmgr writing to /sys/kernel/dlpar (for pHyp partitions)
> or from a hotplug interrupt (for guests). I don't believe the 'removable'
> sysfs file is used in either of these paths by drmgr. The only time it is
> used is on older kernels that do not support in-kernel memory DLPAR.
> Given this, I don't think removing the 'removable' sysfs file would cause any
> issues for the drmgr command. The only scenario I can think of is using an old
> version of drmgr that does not support in-kernel memory DLPAR on a new kernel
> where the 'removable' sysfs file has been removed. This doesn't seem likely
> though and drmgr could be updated to detect this.

Thanks for the information!
Michal Hocko

  reply index

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-24 15:53 David Hildenbrand
2020-01-24 19:10 ` Fontenot, Nathan
2020-01-27  9:23   ` Michal Hocko [this message]
2020-01-27  9:33     ` David Hildenbrand
2020-01-27 13:25       ` Michal Hocko
2020-01-27 15:23       ` Fontenot, Nathan
2020-01-27 13:29 ` Michal Hocko
2020-01-27 13:34   ` David Hildenbrand

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