[PATCH 4/7] Allow sysfs memory directories to be split
nfont at austin.ibm.com
Wed Jul 14 13:18:03 EST 2010
On 07/13/2010 07:35 PM, KAMEZAWA Hiroyuki wrote:
> On Tue, 13 Jul 2010 10:51:58 -0500
> Nathan Fontenot <nfont at austin.ibm.com> wrote:
>>> 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
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.
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