【Linux 内核 内存管理】物理内存组织结构 ④ ( 内存区域 zone 简介 | zone 结构体源码分析 | zone 结构体源码 )
2024-05-20 09:33:06
文章目录
- 一、内存区域 zone 简介
- 二、zone 结构体源码分析
- 1、watermark 成员
- 2、lowmem_reserve 成员
- 3、zone_pgdat 成员
- 4、pageset 成员
- 5、zone_start_pfn 成员
- 6、managed_pages、spanned_pages、present_pages成员
- 7、name 成员
- 8、free_area 成员
- 三、zone 结构体源码
内存管理系统 333级结构 :
① 内存节点 Node ,
② 内存区域 Zone ,
③ 内存页 Page ,
Linux 内核中 , 使用 上述 333 级结构 描述 和 管理 " 物理内存 " ;
一、内存区域 zone 简介
" 内存节点 " 是内存管理的 最顶层结构 ,
" 内存节点 " 再向下划分 , 就是 " 内存区域 " zone ,
" 内存区域 " 在 Linux 内核中使用 struct zone 结构体类型进行描述 , zone 枚举定义在 Linux 内核源码的 linux-4.12\include\linux\mmzone.h#350 位置 ;
每个 " 内存区域 " , 都使用 111 个 zone 结构体 描述 ;
二、zone 结构体源码分析
1、watermark 成员
watermark 表示 " 页分配器 " 使用的 水线 ;
/* zone watermarks, access with *_wmark_pages(zone) macros */unsigned long watermark[NR_WMARK];
2、lowmem_reserve 成员
lowmem_reserve 表示 页分配器 使用的 区域 , 这些区域 必须 保留 , 不能借给高区域类型 ;
/** We don't know if the memory that we're going to allocate will be* freeable or/and it will be released eventually, so to avoid totally* wasting several GB of ram we must reserve some of the lower zone* memory (otherwise we risk to run OOM on the lower zones despite* there being tons of freeable ram on the higher zones). This array is* recalculated at runtime if the sysctl_lowmem_reserve_ratio sysctl* changes.*/long lowmem_reserve[MAX_NR_ZONES];
3、zone_pgdat 成员
zone_pgdat 指向 " 内存节点 " 的 pglist_data 实例 ;
struct pglist_data *zone_pgdat;
4、pageset 成员
pageset 表示 每个 " 处理页 " 的集合 ;
struct per_cpu_pageset __percpu *pageset;
5、zone_start_pfn 成员
zone_start_pfn 表示当前 " 内存区域 zone " 的 " 起始物理页 " 编号 ;
/* zone_start_pfn == zone_start_paddr >> PAGE_SHIFT */unsigned long zone_start_pfn;
6、managed_pages、spanned_pages、present_pages成员
managed_pages 表示 " 伙伴分配器 " 管理的 物理页数量 ;
spanned_pages 表示 当前的 " 内存区域 " 跨越的 物理页 个数 , 包含 " 内存空洞 " ;
present_pages 表示 当前的 " 内存区域 " 包含的 物理页 个数 , 不包含 " 内存空洞 " ;
/** 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(pages in holes);** 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 at runtime should be protected by* mem_hotplug_begin/end(). Any reader who can't tolerant drift of* present_pages should get_online_mems() to get a stable value.** Read access to managed_pages should be safe because it's unsigned* long. Write access to zone->managed_pages and totalram_pages are* protected by managed_page_count_lock at runtime. Idealy only* adjust_managed_page_count() should be used instead of directly* touching zone->managed_pages and totalram_pages.*/unsigned long managed_pages;unsigned long spanned_pages;unsigned long present_pages;
7、name 成员
name 表示 " 内存区域 " 名称 ;
const char *name;
8、free_area 成员
free_area 表示 不同长度的 内存空间区域 ;
/* free areas of different sizes */struct free_area free_area[MAX_ORDER];
三、zone 结构体源码
zone 结构体源码 :
struct zone {/* Read-mostly fields *//* zone watermarks, access with *_wmark_pages(zone) macros */unsigned long watermark[NR_WMARK];unsigned long nr_reserved_highatomic;/** We don't know if the memory that we're going to allocate will be* freeable or/and it will be released eventually, so to avoid totally* wasting several GB of ram we must reserve some of the lower zone* memory (otherwise we risk to run OOM on the lower zones despite* there being tons of freeable ram on the higher zones). This array is* recalculated at runtime if the sysctl_lowmem_reserve_ratio sysctl* changes.*/long lowmem_reserve[MAX_NR_ZONES];#ifdef CONFIG_NUMAint node;
#endifstruct pglist_data *zone_pgdat;struct per_cpu_pageset __percpu *pageset;#ifndef CONFIG_SPARSEMEM/** Flags for a pageblock_nr_pages block. See pageblock-flags.h.* In SPARSEMEM, this map is stored in struct mem_section*/unsigned long *pageblock_flags;
#endif /* CONFIG_SPARSEMEM *//* zone_start_pfn == zone_start_paddr >> PAGE_SHIFT */unsigned long zone_start_pfn;/** 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(pages in holes);** 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 at runtime should be protected by* mem_hotplug_begin/end(). Any reader who can't tolerant drift of* present_pages should get_online_mems() to get a stable value.** Read access to managed_pages should be safe because it's unsigned* long. Write access to zone->managed_pages and totalram_pages are* protected by managed_page_count_lock at runtime. Idealy only* adjust_managed_page_count() should be used instead of directly* touching zone->managed_pages and totalram_pages.*/unsigned long managed_pages;unsigned long spanned_pages;unsigned long present_pages;const char *name;#ifdef CONFIG_MEMORY_ISOLATION/** Number of isolated pageblock. It is used to solve incorrect* freepage counting problem due to racy retrieving migratetype* of pageblock. Protected by zone->lock.*/unsigned long nr_isolate_pageblock;
#endif#ifdef CONFIG_MEMORY_HOTPLUG/* see spanned/present_pages for more description */seqlock_t span_seqlock;
#endifint initialized;/* Write-intensive fields used from the page allocator */ZONE_PADDING(_pad1_)/* free areas of different sizes */struct free_area free_area[MAX_ORDER];/* zone flags, see below */unsigned long flags;/* Primarily protects free_area */spinlock_t lock;/* Write-intensive fields used by compaction and vmstats. */ZONE_PADDING(_pad2_)/** When free pages are below this point, additional steps are taken* when reading the number of free pages to avoid per-cpu counter* drift allowing watermarks to be breached*/unsigned long percpu_drift_mark;#if defined CONFIG_COMPACTION || defined CONFIG_CMA/* pfn where compaction free scanner should start */unsigned long compact_cached_free_pfn;/* pfn where async and sync compaction migration scanner should start */unsigned long compact_cached_migrate_pfn[2];
#endif#ifdef CONFIG_COMPACTION/** On compaction failure, 1<<compact_defer_shift compactions* are skipped before trying again. The number attempted since* last failure is tracked with compact_considered.*/unsigned int compact_considered;unsigned int compact_defer_shift;int compact_order_failed;
#endif#if defined CONFIG_COMPACTION || defined CONFIG_CMA/* Set to true when the PG_migrate_skip bits should be cleared */bool compact_blockskip_flush;
#endifbool contiguous;ZONE_PADDING(_pad3_)/* Zone statistics */atomic_long_t vm_stat[NR_VM_ZONE_STAT_ITEMS];
} ____cacheline_internodealigned_in_smp;
源码路径 : linux-4.12\include\linux\mmzone.h#350
【Linux 内核 内存管理】物理内存组织结构 ④ ( 内存区域 zone 简介 | zone 结构体源码分析 | zone 结构体源码 )相关推荐
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