Re: [PATCH v6 2/5] mm/sparsemem: Defer the ms->section_mem_map clearing

Oscar Salvador
2018-06-28T11:20:02Z

On Thu, Jun 28, 2018 at 02:28:54PM +0800, Baoquan He wrote:
> In sparse_init(), if CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER=y, system
> will allocate one continuous memory chunk for mem maps on one node and
> populate the relevant page tables to map memory section one by one. If
> fail to populate for a certain mem section, print warning and its
> ->section_mem_map will be cleared to cancel the marking of being present.
> Like this, the number of mem sections marked as present could become
> less during sparse_init() execution.
>
> Here just defer the ms->section_mem_map clearing if failed to populate
> its page tables until the last for_each_present_section_nr() loop. This
> is in preparation for later optimizing the mem map allocation.
>
> Signed-off-by: Baoquan He <bhe@redhat.com>
> Reviewed-by: Pavel Tatashin <pasha.tatashin@oracle.com>

Looks good to me.

Reviewed-by: Oscar Salvador <osalvador@suse.de>

> ---
> mm/sparse-vmemmap.c | 4 ----
> mm/sparse.c | 15 ++++++++-------
> 2 files changed, 8 insertions(+), 11 deletions(-)
>
> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> index bd0276d5f66b..68bb65b2d34d 100644
> --- a/mm/sparse-vmemmap.c
> +++ b/mm/sparse-vmemmap.c
> @@ -292,18 +292,14 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
> }
>
> for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
> - struct mem_section *ms;
> -
> if (!present_section_nr(pnum))
> continue;
>
> map_map[pnum] = sparse_mem_map_populate(pnum, nodeid, NULL);
> if (map_map[pnum])
> continue;
> - ms = __nr_to_section(pnum);
> pr_err("%s: sparsemem memory map backing failed some memory will not be available\n",
> __func__);
> - ms->section_mem_map = 0;
> }
>
> if (vmemmap_buf_start) {
> diff --git a/mm/sparse.c b/mm/sparse.c
> index 6314303130b0..6a706093307d 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -441,17 +441,13 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
>
> /* fallback */
> for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
> - struct mem_section *ms;
> -
> if (!present_section_nr(pnum))
> continue;
> map_map[pnum] = sparse_mem_map_populate(pnum, nodeid, NULL);
> if (map_map[pnum])
> continue;
> - ms = __nr_to_section(pnum);
> pr_err("%s: sparsemem memory map backing failed some memory will not be available\n",
> __func__);
> - ms->section_mem_map = 0;
> }
> }
> #endif /* !CONFIG_SPARSEMEM_VMEMMAP */
> @@ -479,7 +475,6 @@ static struct page __init *sparse_early_mem_map_alloc(unsigned long pnum)
>
> pr_err("%s: sparsemem memory map backing failed some memory will not be available\n",
> __func__);
> - ms->section_mem_map = 0;
> return NULL;
> }
> #endif
> @@ -583,17 +578,23 @@ void __init sparse_init(void)
> #endif
>
> for_each_present_section_nr(0, pnum) {
> + struct mem_section *ms;
> + ms = __nr_to_section(pnum);
> usemap = usemap_map[pnum];
> - if (!usemap)
> + if (!usemap) {
> + ms->section_mem_map = 0;
> continue;
> + }
>
> #ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
> map = map_map[pnum];
> #else
> map = sparse_early_mem_map_alloc(pnum);
> #endif
> - if (!map)
> + if (!map) {
> + ms->section_mem_map = 0;
> continue;
> + }
>
> sparse_init_one_section(__nr_to_section(pnum), pnum, map,
> usemap);
> --
> 2.13.6
>

--
Oscar Salvador
SUSE L3