The patch titled
mm: make mem_map allocation continuous
has been added to the -mm tree. Its filename is
mm-make-mem_map-allocation-continuous-v2.patch
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See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: mm: make mem_map allocation continuous
From: Yinghai Lu <yhlu.kernel.send@xxxxxxxxx>
vmemmap allocation current got
[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
...
there is 2M hole between them.
the rootcause is that usemap (24 bytes) will be allocated after every 2M
mem_map. and it will push next vmemmap (2M) to next align (2M).
solution:
try to allocate mem_map continously.
after patch, will 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
...
and usemap will share in 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.
for power pc
Badari Pulavarty <pbadari@xxxxxxxxxx> wrote:
> You have to call sparse_init_one_section() on each pmap and usemap
> as we allocate - since valid_section() depends on it (which is needed
> by vmemmap_populate() to check if the section is populated or not).
> On ppc, we need to call htab_bolted_mapping() on each section and
> we need to skip existing sections.
so try to allocate usemap at first altogether.
Signed-off-by: Yinghai Lu <yhlu.kernel@xxxxxxxxx>
Cc: Andy Whitcroft <apw@xxxxxxxxxxxx>
Cc: Yasunori Goto <y-goto@xxxxxxxxxxxxxx>
Cc: Dave Hansen <haveblue@xxxxxxxxxx>
Cc: Bob Picco <bob.picco@xxxxxx>
Cc: Christoph Lameter <clameter@xxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Badari Pulavarty <pbadari@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/sparse.c | 32 +++++++++++++++++++++++++++++---
1 file changed, 29 insertions(+), 3 deletions(-)
diff -puN mm/sparse.c~mm-make-mem_map-allocation-continuous-v2 mm/sparse.c
--- a/mm/sparse.c~mm-make-mem_map-allocation-continuous-v2
+++ a/mm/sparse.c
@@ -295,22 +295,48 @@ void __init sparse_init(void)
unsigned long pnum;
struct page *map;
unsigned long *usemap;
+ unsigned long **usemap_map;
+ int size;
+
+ /*
+ * map is using big page (aka 2M in x86 64 bit)
+ * usemap is less one page (aka 24 bytes)
+ * so alloc 2M (with 2M align) and 24 bytes in turn will
+ * make next 2M slip to one more 2M later.
+ * then in big system, the memory will have a lot of holes...
+ * here try to allocate 2M pages continously.
+ *
+ * powerpc need to call sparse_init_one_section right after each
+ * sparse_early_mem_map_alloc, so allocate usemap_map at first.
+ */
+ size = sizeof(unsigned long *) * NR_MEM_SECTIONS;
+ usemap_map = alloc_bootmem(size);
+ if (!usemap_map)
+ panic("can not allocate usemap_map\n");
for (pnum = 0; pnum < NR_MEM_SECTIONS; pnum++) {
if (!present_section_nr(pnum))
continue;
+ usemap_map[pnum] = sparse_early_usemap_alloc(pnum);
+ }
- map = sparse_early_mem_map_alloc(pnum);
- if (!map)
+ for (pnum = 0; pnum < NR_MEM_SECTIONS; pnum++) {
+ if (!present_section_nr(pnum))
continue;
- usemap = sparse_early_usemap_alloc(pnum);
+ usemap = usemap_map[pnum];
if (!usemap)
continue;
+ map = sparse_early_mem_map_alloc(pnum);
+ if (!map)
+ continue;
+
sparse_init_one_section(__nr_to_section(pnum), pnum, map,
usemap);
}
+
+ free_bootmem(__pa(usemap_map), size);
}
#ifdef CONFIG_MEMORY_HOTPLUG
_
Patches currently in -mm which might be from yhlu.kernel.send@xxxxxxxxx are
mm-make-mem_map-allocation-continuous-v2.patch
mm-offset-align-in-alloc_bootmem.patch
mm-make-reserve_bootmem-can-crossed-the-nodes.patch
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