Messages in this thread | | | Date | Fri, 10 Oct 2008 16:32:30 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 1/2] [REPOST] mm: show node to memory section relationship with symlinks in sysfs |
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On Fri, 10 Oct 2008 16:18:44 -0700 Gary Hade <garyhade@us.ibm.com> wrote:
> On Fri, Oct 10, 2008 at 02:59:50PM -0700, Andrew Morton wrote: > > On Fri, 10 Oct 2008 14:33:57 -0700 > > Gary Hade <garyhade@us.ibm.com> wrote: > > > > > On Fri, Oct 10, 2008 at 12:42:39PM -0700, Andrew Morton wrote: > > > > On Thu, 9 Oct 2008 12:21:15 -0700 > > > > Gary Hade <garyhade@us.ibm.com> wrote: > > > > > > > > > Show node to memory section relationship with symlinks in sysfs > > > > > > > > > > Add /sys/devices/system/node/nodeX/memoryY symlinks for all > > > > > the memory sections located on nodeX. For example: > > > > > /sys/devices/system/node/node1/memory135 -> ../../memory/memory135 > > > > > indicates that memory section 135 resides on node1. > > > > > > > > I'm not seeing here a description of why the kernel needs this feature. > > > > Why is it useful? How will it be used? What value does it have to > > > > our users? > > > > > > Sorry, I should have included that. In our case, it is another > > > small step towards eventual total node removal. We will need to > > > know which memory sections to offline for whatever node is targeted > > > for removal. However, I suspect that exposing the node to section > > > information to user-level could be useful for other purposes. > > > For example, I have been thinking that using memory hotremove > > > functionality to modify the amount of available memory on specific > > > nodes without having to physically add/remove DIMMs might be useful > > > to those that test application or benchmark performance on a > > > multi-node system in various memory configurations. > > > > > > > hm, OK, thanks. It does sound a bit thin, and if we merge this then > > not only do we get a porkier kernel, > > Would you feel the same about the size increase if patch 2/2 (include > memory section subtree in sysfs with only sparsemem enabled) was > withdrawn? > > Without patch 2/2 the size increase for non-Sparsemem or Sparsemem > wo/memory hotplug kernels is extremely small. Even for memory hotplug > enabled kernels there is only a little extra code in ./drivers/base/node.o > which only gets linked into NUMA enabled kernels. I can gather some numbers > if necessary.
Size is probably a minor issue on memory-hotpluggable machines.
> > we also get a new userspace interface which we're then locked into. > > True.
That's a bigger issue. The later we leave this sort of thing, the more information we have.
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