我在Kubernetes集群中运行我的rethinkdb容器。以下是我注意到的内容:
在CoreOS主机中运行top，rethinkdb进程大约需要3Gb:
$ top
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
981 root 20 0 53.9m 34.5m 20.9m S 15.6 0.4 1153:34 hyperkube
51139 root 20 0 4109.3m 3.179g 22.5m S 15.0 41.8 217:43.56 rethinkdb
579 root 20 0 707.5m 76.1m 19.3m S 2.3 1.0 268:33.55 kubelet
但是运行
docker stats检查rethinkdb容器，大约需要7Gb!$ docker ps | grep rethinkdb
eb9e6b83d6b8 rethinkdb:2.1.5 "rethinkdb --bind al 3 days ago Up 3 days k8s_rethinkdb-3.746aa_rethinkdb-rc-3-eiyt7_default_560121bb-82af-11e5-9c05-00155d070266_661dfae4
$ docker stats eb9e6b83d6b8
CONTAINER CPU % MEM USAGE/LIMIT MEM % NET I/O
eb9e6b83d6b8 4.96% 6.992 GB/8.169 GB 85.59% 0 B/0 B
$ free -m
total used free shared buffers cached
Mem: 7790 7709 81 0 71 3505
-/+ buffers/cache: 4132 3657
Swap: 0 0 0
有人可以解释为什么容器比rethinkdb进程本身占用更多的内存吗？
我正在运行docker v1.7.1，CoreOS v773.1.0，内核4.1.5
最佳答案
在top命令中，您正在查看物理内存量。在stats命令中，这还包括磁盘缓存的ram，因此它总是大于ram的物理量。当您确实需要更多RAM时，将释放缓存的磁盘供应用程序使用。
实际上，内存使用量是通过cgroup memory.usage_in_bytes提取的，您可以在/sys/fs/cgroup/memory/docker/long_container_id/memory.usage_in_bytes中访问它。并根据linux doc https://www.kernel.org/doc/Documentation/cgroups/memory.txt 5.5节:
5.5 usage_in_bytes
For efficiency, as other kernel components, memory cgroup uses some optimization to avoid unnecessary cacheline false sharing. usage_in_bytes is affected by the method and doesn't show 'exact' value of memory (and swap) usage, it's a fuzz value for efficient access. (Of course, when necessary, it's synchronized.) If you want to know more exact memory usage, you should use RSS+CACHE(+SWAP) value in memory.stat(see 5.2).
关于docker - Rethinkdb容器:rethinkdb进程占用的RAM比整个容器少，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/33583407/