Messages in this thread | | | Date | Wed, 24 Jun 2020 09:11:18 +0800 | From | Wei Yang <> | Subject | Re: [PATCH] mm/spase: never partially remove memmap for early section |
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On Tue, Jun 23, 2020 at 05:21:06PM -0700, Dan Williams wrote: >On Tue, Jun 23, 2020 at 2:43 AM Wei Yang ><richard.weiyang@linux.alibaba.com> wrote: >> >> For early sections, we assumes its memmap will never be partially >> removed. But current behavior breaks this. > >Where do we assume that? > >The primary use case for this was mapping pmem that collides with >System-RAM in the same 128MB section. That collision will certainly be >depopulated on-demand depending on the state of the pmem device. So, >I'm not understanding the problem or the benefit of this change.
Hi, Dan
There is a discussion in the thread you just replied:
mm/shuffle: don't move pages between zones and don't read garbage memmaps
Besides this, the comment in section_activate() says:
* The early init code does not consider partially populated * initial sections, it simply assumes that memory will never be * referenced. If we hot-add memory into such a section then we * do not need to populate the memmap and can simply reuse what * is already there.
Per my understanding, if we hot-add then hot-remove the sub-section, we may not have a valid memmep for this part sub-section? Because we depopulate it at hot-remove while we don't populate it when hot-add.
Is my understanding correct?
-- Wei Yang Help you, Help me
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