Messages in this thread | | | Date | Wed, 16 Sep 2020 20:50:41 +0200 | From | osalvador@suse ... | Subject | Re: [PATCH RFC 0/4] mm: place pages to the freelist tail when onling and undoing isolation |
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On 2020-09-16 20:34, David Hildenbrand wrote: > When adding separate memory blocks via add_memory*() and onlining them > immediately, the metadata (especially the memmap) of the next block > will be > placed onto one of the just added+onlined block. This creates a chain > of unmovable allocations: If the last memory block cannot get > offlined+removed() so will all dependant ones. We directly have > unmovable > allocations all over the place. > > This can be observed quite easily using virtio-mem, however, it can > also > be observed when using DIMMs. The freshly onlined pages will usually be > placed to the head of the freelists, meaning they will be allocated > next, > turning the just-added memory usually immediately un-removable. The > fresh pages are cold, prefering to allocate others (that might be hot) > also feels to be the natural thing to do. > > It also applies to the hyper-v balloon xen-balloon, and ppc64 dlpar: > when > adding separate, successive memory blocks, each memory block will have > unmovable allocations on them - for example gigantic pages will fail to > allocate. > > While the ZONE_NORMAL doesn't provide any guarantees that memory can > get > offlined+removed again (any kind of fragmentation with unmovable > allocations is possible), there are many scenarios (hotplugging a lot > of > memory, running workload, hotunplug some memory/as much as possible) > where > we can offline+remove quite a lot with this patchset.
Hi David,
I did not read through the patchset yet, so sorry if the question is nonsense, but is this not trying to fix the same issue the vmemmap patches did? [1]
I was about to give it a new respin now that thw hwpoison stuff has been settled.
[1] https://patchwork.kernel.org/cover/11059175/ >
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