On Thu, 2018-11-22 at 17:48 +0800, Wei Yang wrote:
> When DEFERRED_STRUCT_PAGE_INIT is configured, only the first section of
> each node's highest zone is initialized before defer stage.
>
> static_init_pgcnt is used to store the number of pages like this:
>
> pgdat->static_init_pgcnt = min_t(unsigned long, PAGES_PER_SECTION,
> pgdat->node_spanned_pages);
>
> because we don't want to overflow zone's range.
>
> But this is not necessary, since defer_init() is called like this:
>
> memmap_init_zone()
> for pfn in [start_pfn, end_pfn)
> defer_init(pfn, end_pfn)
>
> In case (pgdat->node_spanned_pages < PAGES_PER_SECTION), the loop would
> stop before calling defer_init().
>
> BTW, comparing PAGES_PER_SECTION with node_spanned_pages is not correct,
> since nr_initialised is zone based instead of node based. Even
> node_spanned_pages is bigger than PAGES_PER_SECTION, its highest zone
> would have pages less than PAGES_PER_SECTION.
>
> Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
This all seems to make sense to me, and appears to be a valid
improvement.
Reviewed-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
> ---
> include/linux/mmzone.h | 2 --
> mm/page_alloc.c | 13 ++++++-------
> 2 files changed, 6 insertions(+), 9 deletions(-)
>
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index ae7a830a21eb..68d7b558924b 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -692,8 +692,6 @@ typedef struct pglist_data {
> * is the first PFN that needs to be initialised.
> */
> unsigned long first_deferred_pfn;
> - /* Number of non-deferred pages */
> - unsigned long static_init_pgcnt;
> #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
>
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 76e12179cd5e..b542d82400cf 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -326,8 +326,13 @@ defer_init(int nid, unsigned long pfn, unsigned long end_pfn)
> /* Always populate low zones for address-constrained allocations */
> if (end_pfn < pgdat_end_pfn(NODE_DATA(nid)))
> return false;
> +
> + /*
> + * We start only with one section of pages, more pages are added as
> + * needed until the rest of deferred pages are initialized.
> + */
> nr_initialised++;
> - if ((nr_initialised > NODE_DATA(nid)->static_init_pgcnt) &&
> + if ((nr_initialised > PAGES_PER_SECTION) &&
> (pfn & (PAGES_PER_SECTION - 1)) == 0) {
> NODE_DATA(nid)->first_deferred_pfn = pfn;
> return true;
> @@ -6451,12 +6456,6 @@ static void __ref alloc_node_mem_map(struct pglist_data *pgdat) { }
> #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
> static inline void pgdat_set_deferred_range(pg_data_t *pgdat)
> {
> - /*
> - * We start only with one section of pages, more pages are added as
> - * needed until the rest of deferred pages are initialized.
> - */
> - pgdat->static_init_pgcnt = min_t(unsigned long, PAGES_PER_SECTION,
> - pgdat->node_spanned_pages);
> pgdat->first_deferred_pfn = ULONG_MAX;
> }
> #else
