Messages in this thread | | | Date | Thu, 10 Jan 2013 16:31:28 +0900 | From | Kamezawa Hiroyuki <> | Subject | Re: [PATCH v6 00/15] memory-hotplug: hot-remove physical memory |
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(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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