Re: [lxc-users] LXD 2.14 - Ubuntu 16.04 - kernel 4.4.0-57-generic - SWAP continuing to grow
On Sat, Jul 15, 2017 at 1:58 AM, Ron Kelley 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 ___ lxc-users mailing list lxc-users@lists.linuxcontainers.org http://lists.linuxcontainers.org/listinfo/lxc-users
Re: [lxc-users] LXD 2.14 - Ubuntu 16.04 - kernel 4.4.0-57-generic - SWAP continuing to grow
I'm using LXC, and I frequently observe some unused containers get swapped out, even though system has plenty of RAM and no RAM limits are set. The only bad effect I observe is couple of seconds delay when you first log into them after some time. I guess it is absolutely normal since kernel tries to maximize amount of memory available for disk caches. If you don't like this behavior, instead of trying to fine tune kernel parameters why not disable swap altogether? Many people run it this way, it's mostly a matter of taste these days. (But first check your software for leaks.) > 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. Did you identify what processes all this virtual memory belongs to? > 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. LXC/LXD is hardly responsible for your app stack memory usage. Either you underestimated it or there's a memory leak somewhere. > 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”. Did your VMs use less memory? I don't think so. Limits could be better enforced, but VMs don't magically give you infinite RAM. -- With Best Regards, Marat Khalili On July 14, 2017 9:58:57 PM GMT+03:00, Ron Kelley 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. >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. > > >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”. > > >-Ron >___ >lxc-users mailing list >lxc-users@lists.linuxcontainers.org >http://lists.linuxcontainers.org/listinfo/lxc-users ___ lxc-users mailing list lxc-users@lists.linuxcontainers.org http://lists.linuxcontainers.org/listinfo/lxc-users
[lxc-users] Network problem - arp not updated
Hi everybody. I would like to use lxc to serve HA for Web service. I've done a POC with an ubuntu 16.04. 2 containers with ephemeral option running nginx. Each of running container mount different /var/www/html directory to serve different default page. This 2 containers names are site1 and site2. The template is debian/stretch/amd64. 1 container runs haproxy configured to check site1 and site2 as backend. Lxc-net is configured to send static ip to the 3 containers. My failover test is :- access haproxy with http client multitimes :ok- stop container site2 :ok- haproxy access still working :ok- run new site2 container. :ok- test haproxy with http client :KO => /o fails, the site2 get request from haproxy but doesn't reply. On site2, the arp table doesn't contain haproxy entry. Everything comes ok if I ping haproxy from site2 container. The arp table is ok and site2 replies normaly. Is this a bug or a known issue ? In lxc or in debian's template ? Thanks a lot for your answers. -- François___ lxc-users mailing list lxc-users@lists.linuxcontainers.org http://lists.linuxcontainers.org/listinfo/lxc-users
Re: [lxc-users] LXD 2.14 - Ubuntu 16.04 - kernel 4.4.0-57-generic - SWAP continuing to grow
Thanks for the great replies. Marat/Fajar: How many servers do you guys have running in production, and what are their characteristics (RAM, CPU, workloads, etc)? I am trying to see if our systems generally align to what you are running. Running without swap seems rather drastic and removes the “safety net” in the case of a bad program. In the end, we must have all containers/processes running 24/7. tldr; After digging into this a bit, it seems “top”, “top”, and “free” report similar swap usage, however, other tools report much less swap usage. I found the following threads on the ‘net which include simple scripts to look in /proc and examine swap usage per process: https://stackoverflow.com/questions/479953/how-to-find-out-which-processes-are-swapping-in-linux https://www.cyberciti.biz/faq/linux-which-process-is-using-swap As some people pointed out, top/htop don’t accurately report the swap usage as they combine a number of memory fields together. And, indeed, running the script in each container (looking at /proc) show markedly different results when all the numbers are added up. For example, the “free” command on one of our servers reports 3G of swap in use, but the script that scans the /proc directory only shows 1.3G of real swap in use. Very odd. All that said, the real issue is to find out if one of our containers/processes has a memory leak (per Marat’s suggestion below). Unfortunately, LXD does not provide an easy way to track per-container stats, thus we must “roll our own” tools. -Ron > On Jul 15, 2017, at 5:11 AM, Marat Khalili wrote: > > I'm using LXC, and I frequently observe some unused containers get swapped > out, even though system has plenty of RAM and no RAM limits are set. The only > bad effect I observe is couple of seconds delay when you first log into them > after some time. I guess it is absolutely normal since kernel tries to > maximize amount of memory available for disk caches. > > If you don't like this behavior, instead of trying to fine tune kernel > parameters why not disable swap altogether? Many people run it this way, it's > mostly a matter of taste these days. (But first check your software for > leaks.) > > > 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. > > Did you identify what processes all this virtual memory belongs to? > > > 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. > > LXC/LXD is hardly responsible for your app stack memory usage. Either you > underestimated it or there's a memory leak somewhere. > > > 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”. > > Did your VMs use less memory? I don't think so. Limits could be better > enforced, but VMs don't magically give you infinite RAM. > -- > > With Best Regards, > Marat Khalili > > On July 14, 2017 9:58:57 PM GMT+03:00, Ron Kelley > 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. 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. > > > 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”. > >
Re: [lxc-users] LXD 2.14 - Ubuntu 16.04 - kernel 4.4.0-57-generic - SWAP continuing to grow
Marat/Fajar: How many servers do you guys have running in production, and what are their characteristics (RAM, CPU, workloads, etc)? I have to admit I'm not running a farm; I administer a few, but they are all different depending on task. Still, even smallest has 64GB RAM. In 2017 the 8GB is small even for user notebook IMO. After digging into this a bit, it seems “top”, “top”, and “free” report similar swap usage, however, other tools report much less swap usage. Yes, this is known, they got confused in containers. Run them on host to produce more meaningful results. All that said, the real issue is to find out if one of our containers/processes has a memory leak (per Marat’s suggestion below). Unfortunately, LXD does not provide an easy way to track per-container stats, thus we must “roll our own” tools. Here's a typical top output (on the host system with 19 LXC containers currently running): top - 16:00:01 up 12 days, 10:35, 5 users, load average: 0.67, 0.58, 0.61 Tasks: 501 total, 2 running, 499 sleeping, 0 stopped, 0 zombie %Cpu(s): 5.8 us, 1.4 sy, 0.0 ni, 91.5 id, 1.1 wa, 0.0 hi, 0.2 si, 0.0 st KiB Mem : 65853268 total, 379712 free, 8100284 used, 57373272 buff/cache KiB Swap: 24986931+total, 24782081+free, 2048496 used. 56852384 avail Mem PID USER PR NIVIRTRESSHR S %CPU %MEM TIME+ COMMAND 6671 root 20 0 5450952 3.728g 1564 S 0.3 5.9 93:14.29 qemu-system-x86 6670 root 20 0 5411084 2.073g 1456 S 0.0 3.3 33:32.07 qemu-system-x86 6979 999 20 0 5251132 244532 19436 S 0.0 0.4 101:47.88 drwcsd.real 4338 lxd 20 0 1968400 229004 8052 S 5.3 0.3 639:52.03 mysqld 8135 root 20 0 6553852 198224 4280 S 0.0 0.3 41:52.66 java 4231 root 20 0 150072 99596 99472 S 0.0 0.2 0:19.43 systemd-journal It shows all processes, including those running in containers (first 5 are). I sorted by RES/%RAM; in your case I'd also try sorting by VIRT. I don't know how to directly find process that occupies much swap, but most likely it will have high RES and VIRT values too. As soon as you find problem processes, it is trivial to find container they run in with ps -AFH or pstree -p on the host system. (Note, that user names and PIDs are different inside and outside of containers, don't rely on them.) I don't have much experience with LXD, but I suppose it's same in this aspect. -- With Best Regards, Marat Khalili On 15/07/17 18:48, Ron Kelley wrote: Thanks for the great replies. Marat/Fajar: How many servers do you guys have running in production, and what are their characteristics (RAM, CPU, workloads, etc)? I am trying to see if our systems generally align to what you are running. Running without swap seems rather drastic and removes the “safety net” in the case of a bad program. In the end, we must have all containers/processes running 24/7. tldr; After digging into this a bit, it seems “top”, “top”, and “free” report similar swap usage, however, other tools report much less swap usage. I found the following threads on the ‘net which include simple scripts to look in /proc and examine swap usage per process: https://stackoverflow.com/questions/479953/how-to-find-out-which-processes-are-swapping-in-linux https://www.cyberciti.biz/faq/linux-which-process-is-using-swap As some people pointed out, top/htop don’t accurately report the swap usage as they combine a number of memory fields together. And, indeed, running the script in each container (looking at /proc) show markedly different results when all the numbers are added up. For example, the “free” command on one of our servers reports 3G of swap in use, but the script that scans the /proc directory only shows 1.3G of real swap in use. Very odd. All that said, the real issue is to find out if one of our containers/processes has a memory leak (per Marat’s suggestion below). Unfortunately, LXD does not provide an easy way to track per-container stats, thus we must “roll our own” tools. -Ron On Jul 15, 2017, at 5:11 AM, Marat Khalili wrote: I'm using LXC, and I frequently observe some unused containers get swapped out, even though system has plenty of RAM and no RAM limits are set. The only bad effect I observe is couple of seconds delay when you first log into them after some time. I guess it is absolutely normal since kernel tries to maximize amount of memory available for disk caches. If you don't like this behavior, instead of trying to fine tune kernel parameters why not disable swap altogether? Many people run it this way, it's mostly a matter of taste these days. (But first check your software for leaks.) 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. Did you id
Re: [lxc-users] LXD 2.14 - Ubuntu 16.04 - kernel 4.4.0-57-generic - SWAP continuing to grow
On Sat, Jul 15, 2017 at 10:48 PM, Ron Kelley wrote: > Thanks for the great replies. > > Marat/Fajar: How many servers do you guys have running in production, and > what are their characteristics (RAM, CPU, workloads, etc)? My biggest production one was AWS r4.16xlarge (almost 500GB memory), though nowadays I mostly use r3.8xlarge (around half the memory, but more cost-efficient). It's running many things from small web servers to large hadoop instances. My smallest production system had 16GB RAM. After some struggles (including testing if swap would help, which did not), in the end I increase its RAM to 128GB. MUCH better. > I am trying to see if our systems generally align to what you are > running. Running without swap seems rather drastic and removes the “safety > net” in the case of a bad program. Which is why I mentioned setting the limits beforehand. For a memory-limited system, you should be able to follow http://digitaloceanvps.blogspot.co.id/2014/04/best-configuration-for-512mb-1gb-ram.html or similar. Though since you said you use nginx, instead of setting appache you should be able to just set php-fpm to use on-demand process manager with a small (2-4) max process. > In the end, we must have all containers/processes running 24/7. > Which is EXACTLY why I disable swap. I do NOT want a misconfigured container dragging others down. And when you configure the applications correctly, each container should stay within its limited memory. Things like 'sudden spike in user access' would slow it down (e.g. due to waiting for php-fpm process becomes available) but it would not create a spike in memory usage. > tldr; > > After digging into this a bit, it seems “top”, “top”, and “free” report > similar swap usage, however, other tools report much less swap usage. I > found the following threads on the ‘net which include simple scripts to > look in /proc and examine swap usage per process: > > https://stackoverflow.com/questions/479953/how-to-find- > out-which-processes-are-swapping-in-linux > https://www.cyberciti.biz/faq/linux-which-process-is-using-swap > > As some people pointed out, top/htop don’t accurately report the swap > usage as they combine a number of memory fields together. And, indeed, > running the script in each container (looking at /proc) show markedly > different results when all the numbers are added up. For example, the > “free” command on one of our servers reports 3G of swap in use, but the > script that scans the /proc directory only shows 1.3G of real swap in use. > Very odd. > > All that said, the real issue is to find out if one of our > containers/processes has a memory leak (per Marat’s suggestion below). > Unfortunately, LXD does not provide an easy way to track per-container > stats, thus we must “roll our own” tools. > > /proc/meminfo (and some other files) in the container is fake. It's created by lxcfs, using numbers from cgroup. cgroup would generally provide accurate info (e.g. 'how much memory is used by processes under this cgroup'). If you're rolling your own tools, read cgroup files directly (e.g. /sys/fs/cgroup/memory/lxc/ ...). In any case, if your tools show memory usage in a container higher than its configured limit, then its perfectly normal that it starts to swap. Even when the host itself still have lots of memory. -- Fajar ___ lxc-users mailing list lxc-users@lists.linuxcontainers.org http://lists.linuxcontainers.org/listinfo/lxc-users
