On Sat, Jul 15, 2017 at 1:58 AM, Ron Kelley <[email protected]> wrote:
> Wondering if anyone else has similar issues. > > We have 5x LXD 2.12 servers running (U16.04 - kernel 4.4.0-57-generic - 8G > RAM, 19G SWAP). Each server is running about 50 LXD containers - Wordpress > w/Nginx and PHP7. The servers have been running for about 15 days now, and > swap space continues to grow. In addition, the kswapd0 process starts > consuming CPU until we flush the system cache via "/bin/echo 3 > > /proc/sys/vm/drop_caches” command. > > Our LXD profile looks like this: > ------------------------- > config: > limits.cpu: "2" > limits.memory: 512MB > limits.memory.swap: "true" > limits.memory.swap.priority: "1" > ------------------------- > > > We also have added these to /etc/sysctl.conf > ------------------------- > vm.swappiness=10 > vm.vfs_cache_pressure=50 > ------------------------- > > A quick “top” output shows plenty of available Memory and buff/cache. On the host? What does top/htop show on the container? > But, for some reason, the system continues to swap out the app. For > example, our “server-4” machine shows 8G total RAM, 500MB free, 2.5G > available, and 5G of buff/cache. Yet, swap is at 5.5GB and has been slowly > growing over the past few days. It seems something is preventing the apps > from using the RAM. > > Even if the host has ample RAM, containers won't be able to use it if their usage is over the limit. Hence why I asked for htop in the container. > > To be honest, we have been battling lots of memory/swap issues using LXD. > We started with no tuning, but the app stack quickly ran out of memory. > After editing the profile to allow 512MB RAM per container (and restarting > the container), the kswapd0 issue happens. Given all the issues we have > had with memory and swap using LXD, we are seriously considering moving > back to the traditional VM approach until LXC/LXD is better “baked”. > > > In the end use whatever works for you. I've had enough problems with swap in the past (non-lxc setup) that nowadays I simply disable swap altogether, and configure my apps (e.g. set max connection, max concurrent process, etc) to be able to live with what they have. -- Fajar
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