On Tue, 13 Jul 2010 22:18:03 -0500 Nathan Fontenot <nf...@austin.ibm.com> wrote:
> On 07/13/2010 07:35 PM, KAMEZAWA Hiroyuki wrote: > > On Tue, 13 Jul 2010 10:51:58 -0500 > > Nathan Fontenot <nf...@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? yes. > 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. > Why per-section memory offlining is provided is for allowing good success-rate of memory offlining. Because memory-hotplug has to "migrate or free" all used page under a section, possibility of memory unplug depends on usage of memory. If a section contains unmovable page(kernel page), we can't offline sectin. For example, comparing 1. offlining 128MB of memory at once 2. offlining 8 chunks of 16MB memory "2" can get very good possibility and system-busy time can be much reduced. IIUC, ppc's 1st requirement is "resizing" not "hot-removing some memory device", "2" is much welcomed. So, some fine-grained interface to section_size is appreciated. So, "multiple operations" is much better than single operation. As I posted show/hide patch, I'm writing it in configfs. I think it meets IBM's requirements. _But_, it's IBM's issue not Fujitsu's. So, final decistion will depend on you guys. Anyway, I don't like a too fancy interface as "split". Thanks, -Kame _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
