On 07/13/2010 07:35 PM, KAMEZAWA Hiroyuki wrote:

On Tue, 13 Jul 2010 10:51:58 -0500
Nathan Fontenot [off-list ref] wrote:

quoted

quoted

And for what purpose this interface is ? Does this split memory block into 2 pieces
of the same size ?? sounds __very__ strange interface to me.

Yes, this splits the memory_block into two blocks of the same size.  This was
suggested as something we may want to do.  From ppc perspective I am not sure we
would use this.

The split functionality is not required.  The main goal of the patch set is to
reduce the number of memory sysfs directories created.  From a ppc perspective
the split functionality is not really needed.

Okay, this is an offer from me.

  1. I think you can add an boot option as "don't create memory sysfs".
     please do.

I posted a patch to do that a week or so ago, it didn't go over very well.

  2. I'd like to write a configfs module for handling memory hotplug even when
     sysfs directroy is not created.
     Because configfs support rmdir/mkdir, the user (ppc's daemon?) has to do
     
     When offlining section X.
     # insmod configfs_memory.ko
     # mount -t configfs none /configfs
     # mkdir /configfs/memoryX
     # echo offline > /configfs/memoryX/state
     # rmdir /configfs/memoryX

  And making this operation as the default bahavior for all arch's memory hotplug may
  be better...

Dave, how do you think ? Because ppc guys uses "probe" interface already,
this can be handled... no ?

ppc would still require the existance of the 'probe' interface.

Are you objecting to the 'split' functionality?  If so I do not see any reason from ppc
perspective that it is needed.  This was something Dave suggested, unless I am missing
something.

Since ppc needs the 'probe' interface in sysfs, and for ppc having mutliple 
memory_block_sections reside under a single memory_block makes memory hotplug
simpler.  On ppc we do emory hotplug operations on an LMB size basis.  With my
patches this now lets us set each memory_block to span an LMB's worth of
memory.  Now we could do emory hotplug in a single operation instead of multiple
operations to offline/online all of the memory sections in an LMB.

Of course the easy solution would be to increase SECTION_SIZE_BITS, but we need
support hardware that can have LMB's from 16 MB to 256 MB in size so the
SECTION_SIZE_BITS value has to remain small. 

One problem is that I don't have enough knowledge about configfs..it seems complex.

Me neither, thoug I will take a look at it.

-Nathan