Re: [PATCH v6 00/15] memory-hotplug: hot-remove physical memory
From: Kamezawa Hiroyuki
Date: Thu Jan 10 2013 - 02:32:33 EST
(2013/01/10 16:14), Glauber Costa wrote:
On 01/10/2013 06:17 AM, Tang Chen wrote:
Note: if the memory provided by the memory device is used by the
kernel, it
can't be offlined. It is not a bug.
Right. But how often does this happen in testing? In other words,
please provide an overall description of how well memory hot-remove is
presently operating. Is it reliable? What is the success rate in
real-world situations?
We test the hot-remove functionality mostly with movable_online used.
And the memory used by kernel is not allowed to be removed.
Can you try doing this using cpusets configured to hardwall ?
It is my understanding that the object allocators will try hard not to
allocate anything outside the walls defined by cpuset. Which means that
if you have one process per node, and they are hardwalled, your kernel
memory will be spread evenly among the machine. With a big enough load,
they should eventually be present in all blocks.
I'm sorry I couldn't catch your point.
Do you want to confirm whether cpuset can work enough instead of ZONE_MOVABLE ?
Or Do you want to confirm whether ZONE_MOVABLE will not work if it's used with cpuset ?
Another question I have for you: Have you considering calling
shrink_slab to try to deplete the caches and therefore free at least
slab memory in the nodes that can't be offlined? Is it relevant?
At this stage, we don't consider to call shrink_slab(). We require
nearly 100% success at offlining memory for removing DIMM.
It's my understanding.
IMHO, I don't think shrink_slab() can kill all objects in a node even
if they are some caches. We need more study for doing that.
Thanks,
-Kame
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