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mm: make mem_map allocation continuous
vmemmap allocation currently has this layout: [ffffe20000000000-ffffe200001fffff] PMD ->ffff810001400000 on node 0 [ffffe20000200000-ffffe200003fffff] PMD ->ffff810001800000 on node 0 [ffffe20000400000-ffffe200005fffff] PMD ->ffff810001c00000 on node 0 [ffffe20000600000-ffffe200007fffff] PMD ->ffff810002000000 on node 0 [ffffe20000800000-ffffe200009fffff] PMD ->ffff810002400000 on node 0 ... note that there is a 2M hole between them - not optimal. the root cause is that usemap (24 bytes) will be allocated after every 2M mem_map, and it will push next vmemmap (2M) to the next (2M) alignment. solution: try to allocate the mem_map continously. after the patch, we get: [ffffe20000000000-ffffe200001fffff] PMD ->ffff810001400000 on node 0 [ffffe20000200000-ffffe200003fffff] PMD ->ffff810001600000 on node 0 [ffffe20000400000-ffffe200005fffff] PMD ->ffff810001800000 on node 0 [ffffe20000600000-ffffe200007fffff] PMD ->ffff810001a00000 on node 0 [ffffe20000800000-ffffe200009fffff] PMD ->ffff810001c00000 on node 0 ... which is the ideal layout. and usemap will share a page because of they are allocated continuously too: sparse_early_usemap_alloc: usemap = ffff810024e00000 size = 24 sparse_early_usemap_alloc: usemap = ffff810024e00080 size = 24 sparse_early_usemap_alloc: usemap = ffff810024e00100 size = 24 sparse_early_usemap_alloc: usemap = ffff810024e00180 size = 24 ... so we make the bootmem allocation more compact and use less memory for usemap => mission accomplished ;-) Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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539a5fe226
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34
mm/sparse.c
34
mm/sparse.c
@ -304,22 +304,48 @@ void __init sparse_init(void)
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unsigned long pnum;
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unsigned long pnum;
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struct page *map;
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struct page *map;
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unsigned long *usemap;
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unsigned long *usemap;
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unsigned long **usemap_map;
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int size;
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/*
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* map is using big page (aka 2M in x86 64 bit)
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* usemap is less one page (aka 24 bytes)
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* so alloc 2M (with 2M align) and 24 bytes in turn will
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* make next 2M slip to one more 2M later.
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* then in big system, the memory will have a lot of holes...
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* here try to allocate 2M pages continously.
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*
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* powerpc need to call sparse_init_one_section right after each
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* sparse_early_mem_map_alloc, so allocate usemap_map at first.
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*/
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size = sizeof(unsigned long *) * NR_MEM_SECTIONS;
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usemap_map = alloc_bootmem(size);
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if (!usemap_map)
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panic("can not allocate usemap_map\n");
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for (pnum = 0; pnum < NR_MEM_SECTIONS; pnum++) {
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for (pnum = 0; pnum < NR_MEM_SECTIONS; pnum++) {
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if (!present_section_nr(pnum))
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if (!present_section_nr(pnum))
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continue;
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continue;
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usemap_map[pnum] = sparse_early_usemap_alloc(pnum);
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}
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for (pnum = 0; pnum < NR_MEM_SECTIONS; pnum++) {
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if (!present_section_nr(pnum))
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continue;
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usemap = usemap_map[pnum];
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if (!usemap)
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continue;
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map = sparse_early_mem_map_alloc(pnum);
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map = sparse_early_mem_map_alloc(pnum);
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if (!map)
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if (!map)
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continue;
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continue;
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usemap = sparse_early_usemap_alloc(pnum);
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if (!usemap)
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continue;
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sparse_init_one_section(__nr_to_section(pnum), pnum, map,
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sparse_init_one_section(__nr_to_section(pnum), pnum, map,
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usemap);
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usemap);
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}
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}
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free_bootmem(__pa(usemap_map), size);
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}
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}
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#ifdef CONFIG_MEMORY_HOTPLUG
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#ifdef CONFIG_MEMORY_HOTPLUG
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