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SubjectRe: [PATCH 3/4] alloc_contig_pages() allocate big chunk memory using migration
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On Fri, Nov 19, 2010 at 5:15 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@jp.fujitsu.com> wrote:
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>
> Add an function to allocate contiguous memory larger than MAX_ORDER.
> The main difference between usual page allocator is that this uses
> memory offline technique (Isolate pages and migrate remaining pages.).
>
> I think this is not 100% solution because we can't avoid fragmentation,
> but we have kernelcore= boot option and can create MOVABLE zone. That
> helps us to allow allocate a contiguous range on demand.

And later we can use compaction and reclaim, too.
So I think this approach is the way we have to go.

>
> The new function is
>
>  alloc_contig_pages(base, end, nr_pages, alignment)
>
> This function will allocate contiguous pages of nr_pages from the range
> [base, end). If [base, end) is bigger than nr_pages, some pfn which
> meats alignment will be allocated. If alignment is smaller than MAX_ORDER,

type meet

> it will be raised to be MAX_ORDER.
>
> __alloc_contig_pages() has much more arguments.
>
>
> Some drivers allocates contig pages by bootmem or hiding some memory
> from the kernel at boot. But if contig pages are necessary only in some
> situation, kernelcore= boot option and using page migration is a choice.
>
> Changelog: 2010-11-19
>  - removed no_search
>  - removed some drain_ functions because they are heavy.
>  - check -ENOMEM case
>
> Changelog: 2010-10-26
>  - support gfp_t
>  - support zonelist/nodemask
>  - support [base, end)
>  - support alignment
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> ---
>  include/linux/page-isolation.h |   15 ++
>  mm/page_alloc.c                |   29 ++++
>  mm/page_isolation.c            |  242 +++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 286 insertions(+)
>
> Index: mmotm-1117/mm/page_isolation.c
> ===================================================================
> --- mmotm-1117.orig/mm/page_isolation.c
> +++ mmotm-1117/mm/page_isolation.c
> @@ -5,6 +5,7 @@
>  #include <linux/mm.h>
>  #include <linux/page-isolation.h>
>  #include <linux/pageblock-flags.h>
> +#include <linux/swap.h>
>  #include <linux/memcontrol.h>
>  #include <linux/migrate.h>
>  #include <linux/memory_hotplug.h>
> @@ -396,3 +397,244 @@ retry:
>        }
>        return 0;
>  }
> +
> +/*
> + * Comparing caller specified [user_start, user_end) with physical memory layout
> + * [phys_start, phys_end). If no intersection is longer than nr_pages, return 1.
> + * If there is an intersection, return 0 and fill range in [*start, *end)

I understand the goal of function.
But comment is rather awkward.

> + */
> +static int
> +__calc_search_range(unsigned long user_start, unsigned long user_end,

Personally, I don't like the function name.
How about "__adjust_search_range"?
But I am not against this name strongly. :)

> +               unsigned long nr_pages,
> +               unsigned long phys_start, unsigned long phys_end,
> +               unsigned long *start, unsigned long *end)
> +{
> +       if ((user_start >= phys_end) || (user_end <= phys_start))
> +               return 1;
> +       if (user_start <= phys_start) {
> +               *start = phys_start;
> +               *end = min(user_end, phys_end);
> +       } else {
> +               *start = user_start;
> +               *end = min(user_end, phys_end);
> +       }
> +       if (*end - *start < nr_pages)
> +               return 1;
> +       return 0;
> +}
> +
> +
> +/**
> + * __alloc_contig_pages - allocate a contiguous physical pages
> + * @base: the lowest pfn which caller wants.
> + * @end:  the highest pfn which caller wants.
> + * @nr_pages: the length of a chunk of pages to be allocated.

the number of pages to be allocated.

> + * @align_order: alignment of start address of returned chunk in order.
> + *   Returned' page's order will be aligned to (1 << align_order).If smaller
> + *   than MAX_ORDER, it's raised to MAX_ORDER.
> + * @node: allocate near memory to the node, If -1, current node is used.
> + * @gfpflag: used to specify what zone the memory should be from.
> + * @nodemask: allocate memory within the nodemask.
> + *
> + * Search a memory range [base, end) and allocates physically contiguous
> + * pages. If end - base is larger than nr_pages, a chunk in [base, end) will
> + * be allocated
> + *
> + * This returns a page of the beginning of contiguous block. At failure, NULL
> + * is returned.
> + *
> + * Limitation: at allocation, nr_pages may be increased to be aligned to
> + * MAX_ORDER before searching a range. So, even if there is a enough chunk
> + * for nr_pages, it may not be able to be allocated. Extra tail pages of
> + * allocated chunk is returned to buddy allocator before returning the caller.
> + */
> +
> +#define MIGRATION_RETRY        (5)
> +struct page *__alloc_contig_pages(unsigned long base, unsigned long end,
> +                       unsigned long nr_pages, int align_order,
> +                       int node, gfp_t gfpflag, nodemask_t *mask)
> +{
> +       unsigned long found, aligned_pages, start;
> +       struct page *ret = NULL;
> +       int migration_failed;
> +       unsigned long align_mask;
> +       struct zoneref *z;
> +       struct zone *zone;
> +       struct zonelist *zonelist;
> +       enum zone_type highzone_idx = gfp_zone(gfpflag);
> +       unsigned long zone_start, zone_end, rs, re, pos;
> +
> +       if (node == -1)
> +               node = numa_node_id();
> +
> +       /* check unsupported flags */
> +       if (gfpflag & __GFP_NORETRY)
> +               return NULL;
> +       if ((gfpflag & (__GFP_WAIT | __GFP_IO | __GFP_FS)) !=
> +               (__GFP_WAIT | __GFP_IO | __GFP_FS))
> +               return NULL;

Why do we have to care about __GFP_IO|__GFP_FS?
If you consider compaction/reclaim later, I am OK.

> +
> +       if (gfpflag & __GFP_THISNODE)
> +               zonelist = &NODE_DATA(node)->node_zonelists[1];
> +       else
> +               zonelist = &NODE_DATA(node)->node_zonelists[0];
> +       /*
> +        * Base/nr_page/end should be aligned to MAX_ORDER
> +        */
> +       found = 0;
> +
> +       if (align_order < MAX_ORDER)
> +               align_order = MAX_ORDER;
> +
> +       align_mask = (1 << align_order) - 1;
> +       /*
> +        * We allocates MAX_ORDER aligned pages and cut tail pages later.
> +        */
> +       aligned_pages = ALIGN(nr_pages, (1 << MAX_ORDER));
> +       /*
> +        * If end - base == nr_pages, we can't search range. base must be
> +        * aligned.
> +        */
> +       if ((end - base == nr_pages) && (base & align_mask))
> +               return NULL;
> +
> +       base = ALIGN(base, (1 << align_order));
> +       if ((end <= base) || (end - base < aligned_pages))
> +               return NULL;
> +
> +       /*
> +        * searching contig memory range within [pos, end).
> +        * pos is updated at migration failure to find next chunk in zone.
> +        * pos is reset to the base at searching next zone.
> +        * (see for_each_zone_zonelist_nodemask in mmzone.h)
> +        *
> +        * Note: we cannot assume zones/nodes are in linear memory layout.
> +        */
> +       z = first_zones_zonelist(zonelist, highzone_idx, mask, &zone);
> +       pos = base;
> +retry:
> +       if (!zone)
> +               return NULL;
> +
> +       zone_start = ALIGN(zone->zone_start_pfn, 1 << align_order);
> +       zone_end = zone->zone_start_pfn + zone->spanned_pages;
> +
> +       /* check [pos, end) is in this zone. */
> +       if ((pos >= end) ||
> +            (__calc_search_range(pos, end, aligned_pages,
> +                       zone_start, zone_end, &rs, &re))) {
> +next_zone:
> +               /* go to the next zone */
> +               z = next_zones_zonelist(++z, highzone_idx, mask, &zone);
> +               /* reset the pos */
> +               pos = base;
> +               goto retry;
> +       }
> +       /* [pos, end) is trimmed to [rs, re) in this zone. */
> +       pos = rs;

The 'pos' doesn't used any more at below.

> +
> +       found = find_contig_block(rs, re, aligned_pages, align_order, zone);
> +       if (!found)
> +               goto next_zone;
> +
> +       /*
> +        * Because we isolated the range, free pages in the range will never
> +        * be (re)allocated. scan_lru_pages() finds the next PG_lru page in
> +        * the range and returns 0 if it reaches the end.
> +        */
> +       migration_failed = 0;
> +       rs = found;
> +       re = found + aligned_pages;
> +       for (rs = scan_lru_pages(rs, re);
> +            rs && rs < re;
> +            rs = scan_lru_pages(rs, re)) {
> +               int rc = do_migrate_range(rs, re);
> +               if (!rc)
> +                       migration_failed = 0;
> +               else {
> +                       /* it's better to try another block ? */
> +                       if (++migration_failed >= MIGRATION_RETRY)
> +                               break;
> +                       if (rc == -EBUSY) {
> +                               /* There are unstable pages.on pagevec. */
> +                               lru_add_drain_all();
> +                               /*
> +                                * there may be pages on pcplist before
> +                                * we mark the range as ISOLATED.
> +                                */
> +                               drain_all_pages();
> +                       } else if (rc == -ENOMEM)
> +                               goto nomem;
> +               }
> +               cond_resched();
> +       }
> +       if (!migration_failed) {
> +               /* drop all pages in pagevec and pcp list */
> +               lru_add_drain_all();
> +               drain_all_pages();
> +       }
> +       /* Check all pages are isolated */
> +       if (test_pages_isolated(found, found + aligned_pages)) {
> +               undo_isolate_page_range(found, aligned_pages);
> +               /*
> +                * We failed at [found...found+aligned_pages) migration.
> +                * "rs" is the last pfn scan_lru_pages() found that the page
> +                * is LRU page. Update pos and try next chunk.
> +                */
> +               pos = ALIGN(rs + 1, (1 << align_order));
> +               goto retry; /* goto next chunk */
> +       }
> +       /*
> +        * OK, here, [found...found+pages) memory are isolated.
> +        * All pages in the range will be moved into the list with
> +        * page_count(page)=1.
> +        */
> +       ret = pfn_to_page(found);
> +       alloc_contig_freed_pages(found, found + aligned_pages, gfpflag);
> +       /* unset ISOLATE */
> +       undo_isolate_page_range(found, aligned_pages);
> +       /* Free unnecessary pages in tail */
> +       for (start = found + nr_pages; start < found + aligned_pages; start++)
> +               __free_page(pfn_to_page(start));
> +       return ret;
> +nomem:
> +       undo_isolate_page_range(found, aligned_pages);
> +       return NULL;
> +}
> +EXPORT_SYMBOL_GPL(__alloc_contig_pages);
> +
> +void free_contig_pages(struct page *page, int nr_pages)
> +{
> +       int i;
> +       for (i = 0; i < nr_pages; i++)
> +               __free_page(page + i);
> +}
> +EXPORT_SYMBOL_GPL(free_contig_pages);
> +
> +/*
> + * Allocated pages will not be MOVABLE but MOVABLE zone is a suitable
> + * for allocating big chunk. So, using ZONE_MOVABLE is a default.
> + */
> +
> +struct page *alloc_contig_pages(unsigned long base, unsigned long end,
> +                       unsigned long nr_pages, int align_order)
> +{
> +       return __alloc_contig_pages(base, end, nr_pages, align_order, -1,
> +                               GFP_KERNEL | __GFP_MOVABLE, NULL);
> +}
> +EXPORT_SYMBOL_GPL(alloc_contig_pages);
> +
> +struct page *alloc_contig_pages_host(unsigned long nr_pages, int align_order)
> +{
> +       return __alloc_contig_pages(0, max_pfn, nr_pages, align_order, -1,
> +                               GFP_KERNEL | __GFP_MOVABLE, NULL);
> +}
> +EXPORT_SYMBOL_GPL(alloc_contig_pages_host);
> +
> +struct page *alloc_contig_pages_node(int nid, unsigned long nr_pages,
> +                               int align_order)
> +{
> +       return __alloc_contig_pages(0, max_pfn, nr_pages, align_order, nid,
> +                       GFP_KERNEL | __GFP_THISNODE | __GFP_MOVABLE, NULL);
> +}
> +EXPORT_SYMBOL_GPL(alloc_contig_pages_node);
> Index: mmotm-1117/include/linux/page-isolation.h
> ===================================================================
> --- mmotm-1117.orig/include/linux/page-isolation.h
> +++ mmotm-1117/include/linux/page-isolation.h
> @@ -32,6 +32,8 @@ test_pages_isolated(unsigned long start_
>  */
>  extern int set_migratetype_isolate(struct page *page);
>  extern void unset_migratetype_isolate(struct page *page);
> +extern void alloc_contig_freed_pages(unsigned long pfn,
> +               unsigned long pages, gfp_t flag);
>
>  /*
>  * For migration.
> @@ -41,4 +43,17 @@ int test_pages_in_a_zone(unsigned long s
>  unsigned long scan_lru_pages(unsigned long start, unsigned long end);
>  int do_migrate_range(unsigned long start_pfn, unsigned long end_pfn);
>
> +/*
> + * For large alloc.
> + */
> +struct page *__alloc_contig_pages(unsigned long base, unsigned long end,
> +                               unsigned long nr_pages, int align_order,
> +                               int node, gfp_t flag, nodemask_t *mask);
> +struct page *alloc_contig_pages(unsigned long base, unsigned long end,
> +                               unsigned long nr_pages, int align_order);
> +struct page *alloc_contig_pages_host(unsigned long nr_pages, int align_order);
> +struct page *alloc_contig_pages_node(int nid, unsigned long nr_pages,
> +               int align_order);
> +void free_contig_pages(struct page *page, int nr_pages);
> +
>  #endif
> Index: mmotm-1117/mm/page_alloc.c
> ===================================================================
> --- mmotm-1117.orig/mm/page_alloc.c
> +++ mmotm-1117/mm/page_alloc.c
> @@ -5447,6 +5447,35 @@ out:
>        spin_unlock_irqrestore(&zone->lock, flags);
>  }
>
> +
> +void alloc_contig_freed_pages(unsigned long pfn,  unsigned long end, gfp_t flag)
> +{
> +       struct page *page;
> +       struct zone *zone;
> +       int order;
> +       unsigned long start = pfn;
> +
> +       zone = page_zone(pfn_to_page(pfn));
> +       spin_lock_irq(&zone->lock);
> +       while (pfn < end) {
> +               VM_BUG_ON(!pfn_valid(pfn));
> +               page = pfn_to_page(pfn);
> +               VM_BUG_ON(page_count(page));
> +               VM_BUG_ON(!PageBuddy(page));
> +               list_del(&page->lru);
> +               order = page_order(page);
> +               zone->free_area[order].nr_free--;
> +               rmv_page_order(page);
> +               __mod_zone_page_state(zone, NR_FREE_PAGES, -(1UL << order));
> +               pfn += 1 << order;
> +       }
> +       spin_unlock_irq(&zone->lock);
> +
> +       /*After this, pages in the range can be freed one be one */
> +       for (pfn = start; pfn < end; pfn++)
> +               prep_new_page(pfn_to_page(pfn), 0, flag);
> +}
> +
>  #ifdef CONFIG_MEMORY_HOTREMOVE
>  /*
>  * All pages in the range must be isolated before calling this.
>
>



--
Kind regards,
Minchan Kim
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