RSS低而AnonPages高，说明匿名页未被进程RSS统计覆盖，常见原因包括内核内存分配、大页、进程退出后页未回收等；需结合/proc/meminfo、slabtop、page_owner、tmpfs检查及THP状态综合排查。
这通常说明系统中存在大量匿名页（anon pages），但这些页面未被任何进程的 RSS 统计覆盖——最常见原因是 内核内存分配（如 slab、page cache 的 anon 部分）、大页（THP）、或进程已退出但页未及时回收。RSS 低而 anon 高，核心矛盾在于：RSS 只统计当前进程映射且活跃的匿名页，不包含内核占用、共享页、延迟释放页等。
查清 anon 页面真实归属
不要只看 /proc/meminfo 的 AnonPages，它只是总和。需逐层下钻：
- 运行
cat /proc/meminfo | grep -E "(AnonPages|Shmem|FilePages|SReclaimable|Slab)"，观察 Shmem（tmpfs/shm）是否异常高——tmpfs 文件会被计入 AnonPages，但不计入任何进程 RSS； - 检查
/sys/kernel/debug/page_owner（需开启 CONFIG_PAGE_OWNER）可追溯每页分配栈，定位内核模块或驱动的匿名页泄漏； - 用
slabtop -o查看 slab 中 anon 相关缓存（如kmalloc-*、page-、anon_vma）是否持续增长； - 运行
echo m > /proc/sysrq-trigger后检查dmesg，确认是否有 page allocation failure 或大量 direct reclaim。
排查 tmpfs 和 POSIX 共享内存
tmpfs 文件（/dev/shm、/run、自定义挂载点）的内容属于匿名页，但归属文件系统而非进程。即使进程已退出，只要文件未 unlink，页就一直驻留：
- 执行
find /dev/shm /run -xdev -type f -ls 2>/dev/null | head -20，看是否有大文件残留； - 用
ipcs -m检查 System V 共享内存段，特别是cpid为 0 或lpid异常的段； - 检查应用是否使用 mmap(MAP_ANONYMOUS|MAP_SHARED) 创建大块共享匿名区，且未 munmap 或未设 close-on-exec 导致子进程继承后泄漏。
检查透明大页（THP）与内存碎片
THP 的 fallback 分配或拆分失败时，可能产生大量孤立的 anon huge page 后备页，RSS 不体现，但计入 AnonPages：
- 查看
cat /sys/kernel/mm/transparent_hugepage/{defrag,enabled}状态； - 检查
/proc/buddyinfo是否存在大量不可用的高阶空闲页（如 order-9+ 缺失），导致 THP 折叠失败、退化为普通页堆积； - 运行
grep -i "thp\|huge" /proc/vmstat，关注pgmajfault、thp_split、thp_collapse_alloc等指标突增情况。
确认是否存在僵尸页或延迟回收
进程 exit 后，其 anon vma 若仍有 page fault 引用（如 core dump 中断、ptrace 暂停、或 cgroup memory.pressure 高导致延迟 LRU 移动），页可能滞留在 inactive anon LRU 链表中：
- 用
cat /proc/vmstat | grep -E "(pgpgin|pgpgout|pgmajfault|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|pgpgout|pgpgin|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