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 [thread overview]
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
SUSE Labs
next prev parent reply other threads:[~2020-01-27 9:23 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-24 15:53 [PATCH RFC] drivers/base/memory.c: indicate all memory blocks as removable 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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