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Re: [PATCH v3 3/6] mm/cma: populate ZONE_CMA

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  Re: [PATCH v3 3/6] mm/cma: populate ZONE_CMA Chen Feng <puck.chen@hisilicon.com> - 2016-06-22 11:30 +0200
    Re: [PATCH v3 3/6] mm/cma: populate ZONE_CMA Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-06-23 05:00 +0200

#1428602 — Re: [PATCH v3 3/6] mm/cma: populate ZONE_CMA

Hello,

On 2016/5/26 14:22, js1304@gmail.com wrote:
> From: Joonsoo Kim <iamjoonsoo.kim@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.kim@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.
> 

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#1429419

On Wed, Jun 22, 2016 at 05:23:06PM +0800, Chen Feng wrote:
> Hello,
> 
> On 2016/5/26 14:22, js1304@gmail.com wrote:
> > From: Joonsoo Kim <iamjoonsoo.kim@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.kim@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.

Before setup_usemap(), range of ZONE_CMA is set conservatively, from
min_start_pfn of the node to max_end_pfn of the node. So,
pageblock_flags will be allocated and assigned properly.

Unfortunately, I found a bug for FLATMEM system. If you'd like to
test ZONE_CMA on FLATMEM system, please apply below one.

Thanks.
------------>8------------
diff --git a/mm/cma.c b/mm/cma.c
index 0c1a72f..6cd2973 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -168,13 +168,6 @@ static int __init cma_init_reserved_areas(void)
                return 0;
 
        for (i = 0; i < cma_area_count; i++) {
-               int ret = cma_activate_area(&cma_areas[i]);
-
-               if (ret)
-                       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)
@@ -191,6 +184,13 @@ static int __init cma_init_reserved_areas(void)
                                        zone->zone_start_pfn;
        }
 
+       for (i = 0; i < cma_area_count; i++) {
+               int ret = cma_activate_area(&cma_areas[i]);
+
+               if (ret)
+                       return ret;
+       }
+
        /*
         * Reserved pages for ZONE_CMA are now activated and this would change
         * ZONE_CMA's managed page counter and other zone's present counter.
-- 
1.9.1

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