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Message-ID: <20180201101641.icoxv2sp6ckrjfxd@node.shutemov.name>
Date: Thu, 1 Feb 2018 13:16:41 +0300
From: "Kirill A. Shutemov" <kirill@...temov.name>
To: Baoquan He <bhe@...hat.com>,
Dave Hansen <dave.hansen@...ux.intel.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
akpm@...ux-foundation.org, kirill.shutemov@...ux.intel.com,
mhocko@...e.com, tglx@...utronix.de, douly.fnst@...fujitsu.com
Subject: Re: [PATCH 2/2] mm/sparse.c: Add nr_present_sections to change the
mem_map allocation
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.
Dave, could you take a look?
>
> Signed-off-by: Baoquan He <bhe@...hat.com>
> ---
> mm/sparse-vmemmap.c | 8 +++++---
> mm/sparse.c | 39 +++++++++++++++++++++++++--------------
> 2 files changed, 30 insertions(+), 17 deletions(-)
>
> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> index 315bea91e276..5bb7b63276b3 100644
> --- a/mm/sparse-vmemmap.c
> +++ b/mm/sparse-vmemmap.c
> @@ -302,6 +302,7 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
> unsigned long pnum;
> unsigned long size = sizeof(struct page) * PAGES_PER_SECTION;
> void *vmemmap_buf_start;
> + int i = 0;
>
> size = ALIGN(size, PMD_SIZE);
> vmemmap_buf_start = __earlyonly_bootmem_alloc(nodeid, size * map_count,
> @@ -312,14 +313,15 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
> vmemmap_buf_end = vmemmap_buf_start + size * map_count;
> }
>
> - for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
> + for (pnum = pnum_begin; pnum < pnum_end && i < map_count; pnum++) {
> struct mem_section *ms;
>
> if (!present_section_nr(pnum))
> continue;
>
> - map_map[pnum] = sparse_mem_map_populate(pnum, nodeid);
> - if (map_map[pnum])
> + i++;
> + map_map[i-1] = sparse_mem_map_populate(pnum, nodeid);
> + if (map_map[i-1])
> continue;
> ms = __nr_to_section(pnum);
> pr_err("%s: sparsemem memory map backing failed some memory will not be available\n",
> diff --git a/mm/sparse.c b/mm/sparse.c
> index 54eba92b72a1..18273261be6d 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -202,6 +202,7 @@ static inline int next_present_section_nr(int section_nr)
> (section_nr <= __highest_present_section_nr)); \
> section_nr = next_present_section_nr(section_nr))
>
> +static int nr_present_sections;
> /* Record a memory area against a node. */
> void __init memory_present(int nid, unsigned long start, unsigned long end)
> {
> @@ -231,6 +232,7 @@ void __init memory_present(int nid, unsigned long start, unsigned long end)
> ms->section_mem_map = sparse_encode_early_nid(nid) |
> SECTION_IS_ONLINE;
> section_mark_present(ms);
> + nr_present_sections++;
> }
> }
> }
> @@ -399,6 +401,7 @@ static void __init sparse_early_usemaps_alloc_node(void *data,
> unsigned long pnum;
> unsigned long **usemap_map = (unsigned long **)data;
> int size = usemap_size();
> + int i = 0;
>
> usemap = sparse_early_usemaps_alloc_pgdat_section(NODE_DATA(nodeid),
> size * usemap_count);
> @@ -407,12 +410,13 @@ static void __init sparse_early_usemaps_alloc_node(void *data,
> return;
> }
>
> - for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
> + for (pnum = pnum_begin; pnum < pnum_end && i < usemap_count; pnum++) {
> if (!present_section_nr(pnum))
> continue;
> - usemap_map[pnum] = usemap;
> + usemap_map[i] = usemap;
> usemap += size;
> - check_usemap_section_nr(nodeid, usemap_map[pnum]);
> + check_usemap_section_nr(nodeid, usemap_map[i]);
> + i++;
> }
> }
>
> @@ -440,13 +444,15 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
> void *map;
> unsigned long pnum;
> unsigned long size = sizeof(struct page) * PAGES_PER_SECTION;
> + int i;
>
> map = alloc_remap(nodeid, size * map_count);
> if (map) {
> - for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
> + i = 0;
> + for (pnum = pnum_begin; pnum < pnum_end && i < map_count; pnum++) {
> if (!present_section_nr(pnum))
> continue;
> - map_map[pnum] = map;
> + map_map[i] = map;
> map += size;
> }
> return;
> @@ -457,23 +463,26 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
> PAGE_SIZE, __pa(MAX_DMA_ADDRESS),
> BOOTMEM_ALLOC_ACCESSIBLE, nodeid);
> if (map) {
> - for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
> + i = 0;
> + for (pnum = pnum_begin; pnum < pnum_end && i < map_count; pnum++) {
> if (!present_section_nr(pnum))
> continue;
> - map_map[pnum] = map;
> + map_map[i] = map;
> map += size;
> }
> return;
> }
>
> /* fallback */
> - for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
> + i = 0;
> + for (pnum = pnum_begin; pnum < pnum_end && i < map_count; pnum++) {
> struct mem_section *ms;
>
> if (!present_section_nr(pnum))
> continue;
> - map_map[pnum] = sparse_mem_map_populate(pnum, nodeid);
> - if (map_map[pnum])
> + i++;
> + map_map[i-1] = sparse_mem_map_populate(pnum, nodeid);
> + if (map_map[i-1])
> continue;
> ms = __nr_to_section(pnum);
> pr_err("%s: sparsemem memory map backing failed some memory will not be available\n",
> @@ -552,6 +561,7 @@ static void __init alloc_usemap_and_memmap(void (*alloc_func)
> /* new start, update count etc*/
> nodeid_begin = nodeid;
> pnum_begin = pnum;
> + data += map_count;
> map_count = 1;
> }
> /* ok, last chunk */
> @@ -570,6 +580,7 @@ void __init sparse_init(void)
> unsigned long *usemap;
> unsigned long **usemap_map;
> int size;
> + int i = 0;
> #ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
> int size2;
> struct page **map_map;
> @@ -592,7 +603,7 @@ void __init sparse_init(void)
> * 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;
> + size = sizeof(unsigned long *) * nr_present_sections;
> usemap_map = memblock_virt_alloc(size, 0);
> if (!usemap_map)
> panic("can not allocate usemap_map\n");
> @@ -600,7 +611,7 @@ void __init sparse_init(void)
> (void *)usemap_map);
>
> #ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
> - size2 = sizeof(struct page *) * NR_MEM_SECTIONS;
> + size2 = sizeof(struct page *) * nr_present_sections;
> map_map = memblock_virt_alloc(size2, 0);
> if (!map_map)
> panic("can not allocate map_map\n");
> @@ -611,7 +622,7 @@ void __init sparse_init(void)
> for_each_present_section_nr(0, pnum) {
> struct mem_section *ms;
> ms = __nr_to_section(pnum);
> - usemap = usemap_map[pnum];
> + usemap = usemap_map[i];
> if (!usemap) {
> #ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
> ms->section_mem_map = 0;
> @@ -620,7 +631,7 @@ void __init sparse_init(void)
> }
>
> #ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
> - map = map_map[pnum];
> + map = map_map[i];
> #else
> map = sparse_early_mem_map_alloc(pnum);
> #endif
> --
> 2.13.6
>
> --
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--
Kirill A. Shutemov
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