diff options
Diffstat (limited to 'include/linux/mmzone.h')
| -rw-r--r-- | include/linux/mmzone.h | 50 |
1 files changed, 34 insertions, 16 deletions
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index a23923ba8263..cd55dad56aac 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -63,10 +63,8 @@ enum { #ifdef CONFIG_CMA # define is_migrate_cma(migratetype) unlikely((migratetype) == MIGRATE_CMA) -# define cma_wmark_pages(zone) zone->min_cma_pages #else # define is_migrate_cma(migratetype) false -# define cma_wmark_pages(zone) 0 #endif #define for_each_migratetype_order(order, type) \ @@ -383,13 +381,6 @@ struct zone { /* see spanned/present_pages for more description */ seqlock_t span_seqlock; #endif -#ifdef CONFIG_CMA - /* - * CMA needs to increase watermark levels during the allocation - * process to make sure that the system is not starved. - */ - unsigned long min_cma_pages; -#endif struct free_area free_area[MAX_ORDER]; #ifndef CONFIG_SPARSEMEM @@ -469,17 +460,44 @@ struct zone { unsigned long zone_start_pfn; /* - * zone_start_pfn, spanned_pages and present_pages are all - * protected by span_seqlock. It is a seqlock because it has - * to be read outside of zone->lock, and it is done in the main - * allocator path. But, it is written quite infrequently. + * spanned_pages is the total pages spanned by the zone, including + * holes, which is calculated as: + * spanned_pages = zone_end_pfn - zone_start_pfn; + * + * present_pages is physical pages existing within the zone, which + * is calculated as: + * present_pages = spanned_pages - absent_pages(pags in holes); * - * The lock is declared along with zone->lock because it is + * managed_pages is present pages managed by the buddy system, which + * is calculated as (reserved_pages includes pages allocated by the + * bootmem allocator): + * managed_pages = present_pages - reserved_pages; + * + * So present_pages may be used by memory hotplug or memory power + * management logic to figure out unmanaged pages by checking + * (present_pages - managed_pages). And managed_pages should be used + * by page allocator and vm scanner to calculate all kinds of watermarks + * and thresholds. + * + * Locking rules: + * + * zone_start_pfn and spanned_pages are protected by span_seqlock. + * It is a seqlock because it has to be read outside of zone->lock, + * and it is done in the main allocator path. But, it is written + * quite infrequently. + * + * The span_seq lock is declared along with zone->lock because it is * frequently read in proximity to zone->lock. It's good to * give them a chance of being in the same cacheline. + * + * Write access to present_pages and managed_pages at runtime should + * be protected by lock_memory_hotplug()/unlock_memory_hotplug(). + * Any reader who can't tolerant drift of present_pages and + * managed_pages should hold memory hotplug lock to get a stable value. */ - unsigned long spanned_pages; /* total size, including holes */ - unsigned long present_pages; /* amount of memory (excluding holes) */ + unsigned long spanned_pages; + unsigned long present_pages; + unsigned long managed_pages; /* * rarely used fields: |