linux-kernel - Re: [RFC patch] delete improper hot pluggable code of memory affinity

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Message-Id: <20090717151118.38BC.E1E9C6FF@jp.fujitsu.com>
Date:	Fri, 17 Jul 2009 15:20:53 +0900
From:	Yasunori Goto <y-goto@...fujitsu.com>
To:	Luming Yu <luming.yu@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC patch] delete improper hot pluggable code of memory affinity

> On Fri, Jul 17, 2009 at 1:52 PM, Yasunori Goto<y-goto@...fujitsu.com> wrote:
> >> Without a fix like my proposal, I have seen NUMA configure disabled by
> >> kernel (due to the code the patch deletes) on a system with Enabled
> >> bit set , and Hotplug-able bit cleared, and
> >> CONFIG_MEMORY_HOTPLUG_SPARSE disabled.
> >
> > Ok. I guess that save_add_info() was to check percentage of
> > reserve area when CONFIG_MEMORY_HOTPLUG_RESERVE is set.
> > Its code was removed at 2.6.25, save_add_info() may be garbage now.
> >
> > However, I have one question now.
> >
> >>> - ? ?if (ma->flags & ACPI_SRAT_MEM_HOT_PLUGGABLE) {
> >>> - ? ? ? ? ? ?update_nodes_add(node, start, end);
> >>> - ? ? ? ? ? ?/* restore nodes[node] */
> >>> - ? ? ? ? ? ?*nd = oldnode;
> >>> - ? ? ? ? ? ?if ((nd->start | nd->end) == 0)
> >>> - ? ? ? ? ? ? ? ? ? ?node_clear(node, nodes_parsed);
> >>> - ? ? }
> >
> > I don't understand why you remove this code. could you tell me why?
> 
> Good question. This is exactly the place I'm puzzled too.
> Without delete this code, I still see one fake node instead of 4 real node...
> I think a flow up patch is needed here...

In my understanding, here is for the case when the SRAT entry is enabled,
but memory is not connected. (This is why I sent the first mail).
However, here may have a bug yet. 

I would like to test here, but I don't have a real x86-64 machine which can
hot add memory. So, I can just guess now.

Anyway, thanks for your notification. If you have progress about it,
please let me know.

Bye.

-- 
Yasunori Goto 


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