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? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
