Re: [PATCH RFC] drivers/base/memory.c: indicate all memory blocks as removable

[Michal Hocko]

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