On Wednesday 17 March 2010 19:47:55 Prarit Bhargava wrote:
>
> Thomas Renninger wrote:
> > On Thursday 11 March 2010 09:32:09 chen gong wrote:
> >
> >> On 2010-3-11 16:07, ykzhao wrote:
> >>
> > ...
> >
> >> BTW, how about using UDEV rules to do this operation. It looks more smooth. I know some
> >> Novell guy is working on it.
> >>
> > I also know this guy :)
> >
> > These would be the udev rules to automatically add memory/cpus:
> > SUBSYSTEM=="cpu", ACTION=="add", TEST=="online", ATTR{online}=="0", ATTR{online}="1", RUN+="/bin/logger onlining cpu: $env{DEVPATH}"
> > SUBSYSTEM=="memory", ACTION=="add", TEST=="state", ATTR{state}=="offline", ATTR{state}="online", RUN+="/bin/logger onlining memory: $env{DEVPATH}"
> >
> > But this should be the same as you suggest (at least the memory rule)
> > to do in the kernel:
> > automatically online the memory, once hotadded.
> >
> > I would not add any udev rules before this does not work
> > reliably and currently it is totally broken, mainly because:
> > - not being able to alloc memory on foreign nodes (at least with slab)
> > - C-state, throttling and cpufreq set up is done without valid
> > cpu_data(new_cpu) resulting in wrong C-state (and other) info
> >
> >
>
> Thomas, forgive my ignorance of udev rules ... but can one udev rule
> block another? ... That's not the best way to explain it ... here's an
> example:
>
> CPU hot add on Nehalem-EX. Memory is brought online. Memory udev
> events are generated. CPU udev events are generated.
>
> Can the memory udev events block the cpu udev events? ie) can I be
> assured that memory will come online before the cpus?
I give up, there are too many open issues.
Onlining cpus and memory in parallel currently is not a good idea.
If the cpu event comes first, you run into other issues. I accidently had
the acpi_memhotplug driver not loaded, in this case a new node was not
created at all and the cpus ended up on the wrong node.
Some comments on your patch:
Your patch misses EXPORT_SYMBOL(_GPL?)(set_memory_state); (I wonder why
drivers/base/memory.c does not export symbols under gpl...) and
EXPORT_SYMBOL_GPL(online_pages);
You also need to set each memory block MEM_ONLINE somehow,
while all memory was active, only one memory block showed "online" here:
/sys/devices/system/node/node3/memory*/state
which has side-effects.
Would be great if you add me to CC if you repost or on related topics.
Thanks,
Thomas
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