Messages in this thread | | | Date | Wed, 1 Dec 2010 17:21:48 -0800 (PST) | From | David Rientjes <> | Subject | Re: [8/8, v6] NUMA Hotplug Emulator: implement debugfs interface for memory probe |
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On Thu, 2 Dec 2010, Shaohui Zheng wrote:
> > > From: Shaohui Zheng <shaohui.zheng@intel.com> > > > > > > Implement a debugfs inteface /sys/kernel/debug/mem_hotplug/probe for meomory hotplug > > > emulation. it accepts the same parameters like > > > /sys/devices/system/memory/probe. > > > > > > > NACK, we don't need two interfaces to do the same thing. > > You may not know the background, the sysfs memory/probe interface is a general > interface. Even through we have a debugfs interface, we should still keep it. > > For test purpose, the sysfs is enough, according to the comments from Greg & Dave, > we create the debugfs interface. >
I doubt either Greg or Dave suggested adding duplicate interfaces for the same functionality.
The difference is that we needed to add the add_node interface in a new mem_hotplug debugfs directory because it's only useful for debugging kernel code and, thus, doesn't really have an appropriate place in sysfs. Nobody is going to use add_node unless they lack hotpluggable memory sections in their SRAT and want to debug the memory hotplug callers. For example, I already wrote all of this node hotplug emulation stuff when I wrote the node hotplug support for SLAB.
Memory hotplug, however, does serve a non-debugging function and is appropriate in sysfs since this is how people hotplug memory. It's an ABI that we can't simply remove without deprecation over a substantial period of time and in this case it doesn't seem to have a clear advantage. We need not add special emulation support for something that is already possible for real systems, so adding a duplicate interface in debugfs is inappropriate.
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