Messages in this thread | | | Subject | Re: [PATCH 2/2] mm/sparse.c: Add nr_present_sections to change the mem_map allocation | From | Dave Hansen <> | Date | Thu, 1 Feb 2018 05:49:50 -0800 |
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On 02/01/2018 02:16 AM, Kirill A. Shutemov wrote: > On Thu, Feb 01, 2018 at 03:19:56PM +0800, Baoquan He wrote: >> In sparse_init(), we allocate usemap_map and map_map which are pointer >> array with the size of NR_MEM_SECTIONS. The memory consumption can be >> ignorable in 4-level paging mode. While in 5-level paging, this costs >> much memory, 512M. Kdump kernel even can't boot up with a normal >> 'crashkernel=' setting. >> >> Here add a new variable to record the number of present sections. Let's >> allocate the usemap_map and map_map with the size of nr_present_sections. >> We only need to make sure that for the ith present section, usemap_map[i] >> and map_map[i] store its usemap and mem_map separately. >> >> This change can save much memory on most of systems. Anytime, we should >> avoid to define array or allocate memory with the size of NR_MEM_SECTIONS. > That's very desirable outcome. But I don't know much about sparsemem.
... with the downside being that we can no longer hot-add memory that was not part of the original, present sections.
Is that OK?
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