Messages in this thread | | | Date | Wed, 24 Nov 2010 09:20:03 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH 3/4] alloc_contig_pages() allocate big chunk memory using migration |
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On Mon, 22 Nov 2010 20:44:03 +0900 Minchan Kim <minchan.kim@gmail.com> wrote:
> 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 > will fix.
> > 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. >
ok, I will rewrite.
> > + */ > > +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. :) > I will rename this.
> > + 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. > ok.
> > + * @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. > because in page migration, we use GFP_HIGHUSER_MOVABLE now.
> > + > > + 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. > Ah, yes. I'll check this was for what and remove this.
Thanks, -Kame
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