Hello,
On 2016/5/26 14:22, js1...@gmail.com wrote:
> From: Joonsoo Kim <iamjoonsoo....@lge.com>
>
> Until now, reserved pages for CMA are managed in the ordinary zones
> where page's pfn are belong to. This approach has numorous problems
> and fixing them isn't easy. (It is mentioned on previous patch.)
> To fix this situation, ZONE_CMA is introduced in previous patch, but,
> not yet populated. This patch implement population of ZONE_CMA
> by stealing reserved pages from the ordinary zones.
>
> Unlike previous implementation that kernel allocation request with
> __GFP_MOVABLE could be serviced from CMA region, allocation request only
> with GFP_HIGHUSER_MOVABLE can be serviced from CMA region in the new
> approach. This is an inevitable design decision to use the zone
> implementation because ZONE_CMA could contain highmem. Due to this
> decision, ZONE_CMA will work like as ZONE_HIGHMEM or ZONE_MOVABLE.
>
> I don't think it would be a problem because most of file cache pages
> and anonymous pages are requested with GFP_HIGHUSER_MOVABLE. It could
> be proved by the fact that there are many systems with ZONE_HIGHMEM and
> they work fine. Notable disadvantage is that we cannot use these pages
> for blockdev file cache page, because it usually has __GFP_MOVABLE but
> not __GFP_HIGHMEM and __GFP_USER. But, in this case, there is pros and
> cons. In my experience, blockdev file cache pages are one of the top
> reason that causes cma_alloc() to fail temporarily. So, we can get more
> guarantee of cma_alloc() success by discarding that case.
>
> Implementation itself is very easy to understand. Steal when cma area is
> initialized and recalculate various per zone stat/threshold.
>
> Signed-off-by: Joonsoo Kim <iamjoonsoo....@lge.com>
> ---
> include/linux/memory_hotplug.h | 3 ---
> mm/cma.c | 41 +++++++++++++++++++++++++++++++++++++++++
> mm/internal.h | 3 +++
> mm/page_alloc.c | 26 ++++++++++++++++++++++++--
> 4 files changed, 68 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index a864d79..6fde69b 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -198,9 +198,6 @@ void put_online_mems(void);
> void mem_hotplug_begin(void);
> void mem_hotplug_done(void);
>
> -extern void set_zone_contiguous(struct zone *zone);
> -extern void clear_zone_contiguous(struct zone *zone);
> -
> #else /* ! CONFIG_MEMORY_HOTPLUG */
> /*
> * Stub functions for when hotplug is off
> diff --git a/mm/cma.c b/mm/cma.c
> index ea506eb..8684f50 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -38,6 +38,7 @@
> #include <trace/events/cma.h>
>
> #include "cma.h"
> +#include "internal.h"
>
> struct cma cma_areas[MAX_CMA_AREAS];
> unsigned cma_area_count;
> @@ -145,6 +146,11 @@ err:
> static int __init cma_init_reserved_areas(void)
> {
> int i;
> + struct zone *zone;
> + unsigned long start_pfn = UINT_MAX, end_pfn = 0;
> +
> + if (!cma_area_count)
> + return 0;
>
> for (i = 0; i < cma_area_count; i++) {
> int ret = cma_activate_area(&cma_areas[i]);
> @@ -153,6 +159,41 @@ static int __init cma_init_reserved_areas(void)
> return ret;
> }
>
> + for (i = 0; i < cma_area_count; i++) {
> + if (start_pfn > cma_areas[i].base_pfn)
> + start_pfn = cma_areas[i].base_pfn;
> + if (end_pfn < cma_areas[i].base_pfn + cma_areas[i].count)
> + end_pfn = cma_areas[i].base_pfn + cma_areas[i].count;
> + }
> +
> + for_each_populated_zone(zone) {
> + if (!is_zone_cma(zone))
> + continue;
> +
> + /* ZONE_CMA doesn't need to exceed CMA region */
> + zone->zone_start_pfn = max(zone->zone_start_pfn, start_pfn);
> + zone->spanned_pages = min(zone_end_pfn(zone), end_pfn) -
> + zone->zone_start_pfn;
> + }
> +
> + /*
> + * Reserved pages for ZONE_CMA are now activated and this would change
> + * ZONE_CMA's managed page counter and other zone's present counter.
> + * We need to re-calculate various zone information that depends on
> + * this initialization.
> + */
> + build_all_zonelists(NULL, NULL);
> + for_each_populated_zone(zone) {
> + zone_pcp_update(zone);
> + set_zone_contiguous(zone);
> + }
> +
> + /*
> + * We need to re-init per zone wmark by calling
> + * init_per_zone_wmark_min() but doesn't call here because it is
> + * registered on module_init and it will be called later than us.
> + */
> +
> return 0;
> }
> core_initcall(cma_init_reserved_areas);
> diff --git a/mm/internal.h b/mm/internal.h
> index b6ead95..4c37234 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -155,6 +155,9 @@ extern void __free_pages_bootmem(struct page *page,
> unsigned long pfn,
> extern void prep_compound_page(struct page *page, unsigned int order);
> extern int user_min_free_kbytes;
>
> +extern void set_zone_contiguous(struct zone *zone);
> +extern void clear_zone_contiguous(struct zone *zone);
> +
> #if defined CONFIG_COMPACTION || defined CONFIG_CMA
>
> /*
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 0197d5d..796b271 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1572,16 +1572,38 @@ void __init page_alloc_init_late(void)
> }
>
> #ifdef CONFIG_CMA
> +static void __init adjust_present_page_count(struct page *page, long count)
> +{
> + struct zone *zone = page_zone(page);
> +
> + /* We don't need to hold a lock since it is boot-up process */
> + zone->present_pages += count;
> +}
> +
> /* Free whole pageblock and set its migration type to MIGRATE_CMA. */
> void __init init_cma_reserved_pageblock(struct page *page)
> {
> unsigned i = pageblock_nr_pages;
> + unsigned long pfn = page_to_pfn(page);
> struct page *p = page;
> + int nid = page_to_nid(page);
> +
> + /*
> + * ZONE_CMA will steal present pages from other zones by changing
> + * page links so page_zone() is changed. Before that,
> + * we need to adjust previous zone's page count first.
> + */
> + adjust_present_page_count(page, -pageblock_nr_pages);
>
> do {
> __ClearPageReserved(p);
> set_page_count(p, 0);
> - } while (++p, --i);
> +
> + /* Steal pages from other zones */
> + set_page_links(p, ZONE_CMA, nid, pfn);
> + } while (++p, ++pfn, --i);
> +
> + adjust_present_page_count(page, pageblock_nr_pages);
>
> set_pageblock_migratetype(page, MIGRATE_CMA);
The ZONE_CMA should depends on sparse_mem.
Because the zone size is not fixed when init the buddy core.
The pageblock_flags will be NULL when setup_usemap.
>
> @@ -7545,7 +7567,7 @@ void free_contig_range(unsigned long pfn, unsigned
> nr_pages)
> }
> #endif
>
> -#ifdef CONFIG_MEMORY_HOTPLUG
> +#if defined CONFIG_MEMORY_HOTPLUG || defined CONFIG_CMA
> /*
> * The zone indicated has a new number of managed_pages; batch sizes and
> percpu
> * page high values need to be recalulated.
>
