On 03/23/2016 12:10 PM, Peter Steele wrote: > Has anyone seen this issue? We're running containers under CentOS 7.2 and some > of these containers are reporting incorrect memory allocation in > /proc/meminfo. The output below comes from a system with 32G of memory and > 84GB of swap. The values reported are completely wrong. > There was a meminfo bug here: https://bugzilla.redhat.com/show_bug.cgi?id=1300781 The initial report is fixed in git, however the reporter also mentioned the issue you are seeing. I suspect something is going wacky with the memory values we are getting from host cgroups after some period of time. If you can reproduce with Fedora (or RHEL) try filing a bug there - Cole

Even if you don't reproduce on RHEL/Fedora, it would be useful if you figure out exactly what steps it takes to reproduce: is it random, or after a set amount of time, or after machine suspends, or some manual way to tickle the issue. Thanks, Cole

use libvirt 1.3.2, it's more stable and never show negative values for memory and swap inside container

> The latest version available for CentOS/RHEL is version 1.2.17. What > site are you using to get the rpm for version 1.3.2?

I found a download for this version and tried it out but we ran into a different set of problems when running our software in containers under this environment. Unfortunately we're out of time to address these 7.2 issues, so for now we're rolling everything back to 7.1 and will postpone 7.2 tests until our next release cycle starts.

>> I found a download for this version and tried it out but we ran into a >> different set of problems when running our software in containers under >> this environment. What kind problem ? Network ?

Now reporduced with 100% 1) create contrainer with memory limit 1Gb 2) run inside simple memory test allocator: #include <malloc.h> #include <unistd.h> #include <memory.h> #define MB 1024 * 1024 int main() { int total = 0; while (1) { void *p = malloc( 100*MB ); memset(p,0, 100*MB ); total = total + 100; printf("Alloc %d Mb\n",total); sleep(1); } } [root@tst-mxs2 ~]# free total used free shared buff/cache available Mem: 1048576 7412 1028644 11112 12520 1028644 Swap: 1048576 0 1048576 [root@tst-mxs2 ~]# ./a.out Alloc 100 Mb Alloc 200 Mb Alloc 300 Mb Alloc 400 Mb Alloc 500 Mb Alloc 600 Mb Alloc 700 Mb Alloc 800 Mb Alloc 900 Mb Alloc 1000 Mb Killed As You can see, limit worked and "free" inside container show correct values 3) Check situation outside container, from top hadrware node: [root@node01]# cat /sys/fs/cgroup/memory/machine.slice/machine-lxc\\x2d7445\\x2dtst\\x2dmxs2.test.scope/memory.limit_in_bytes 1073741824 4) Check list of pid in cgroups (it's IMPOTANT moment): [root@node01]# cat /sys/fs/cgroup/memory/machine.slice/machine-lxc\\x2d7445\\x2dtst\\x2dmxs2.test.scope/tasks 7445 7446 7480 7506 7510 7511 7512 7529 7532 7533 7723 7724 8251 8253 10455 First PID 7445 - it's pid of libvirt process for container: # ps ax | grep 7445 7445 ? Sl 0:00 /usr/libexec/libvirt_lxc --name tst-mxs2.test --console 21 --security=none --handshake 24 --veth macvlan5 [root@node01]# virsh list Id Name State ---------------------------------------------------- 7445 tst-mxs2.test running 5) Now broke /proc/meminfo inside container. prepare simple systemd service: # cat /usr/lib/systemd/system/true.service [Unit] Description=simple test [Service] Type=simple ExecStart=/bin/true [Install] WantedBy=multi-user.target Enable service first time, disable and start: [root@node01]# systemctl enable /usr/lib/systemd/system/true.service Created symlink from /etc/systemd/system/multi-user.target.wants/true.service to /usr/lib/systemd/system/true.service. [root@node01]# systemctl disable true.service Removed symlink /etc/systemd/system/multi-user.target.wants/true.service. [root@node01]# systemctl start true.service Now check memory inside container: [root@tst-mxs2 ~]# free total used free shared buff/cache available Mem: 9007199254740991 190824 9007199254236179 11112 313988 9007199254236179 Swap: 0 6) Check tasks list in cgroups: [root@node01]# cat /sys/fs/cgroup/memory/machine.slice/machine-lxc\\x2d7445\\x2dtst\\x2dmxs2.test.scope/tasks 7446 7480 7506 7510 7511 7512 7529 7532 7533 7723 7724 8251 8253 After start disabled systemd service, from task list removed libvirt PID 7445. It's mean that inside LXC limit real still worked, 7446 - it's PID of /sbin/init inside container. Check that limit work: [root@tst-mxs2 ~]# free total used free shared buff/cache available Mem: 9007199254740991 190824 9007199254236179 11112 313988 9007199254236179 Swap: 0 0 0 [root@tst-mxs2 ~]# ./a.out Alloc 100 Mb Alloc 200 Mb Alloc 300 Mb Alloc 400 Mb Alloc 500 Mb Alloc 600 Mb Alloc 700 Mb Alloc 800 Mb Alloc 900 Mb Alloc 1000 Mb Killed Broken only fuse mount. It's positive news - process inside container even in case 8Ptb can't allocate more memory that set in cgroups. But negative news - that some java based sotfware (as puppetdb in our case) plan self strategy based on 8Ptb memory and collapsed after reach real limit. resume: 1) don't start disabled service by systemd 2) workaround by cglassify or by it's simple analog [root@node01]# echo 7445 > /sys/fs/cgroup/memory/machine.slice/machine-lxc\\x2d7445\\x2dtst\\x2dmxs2.test.scope/tasks p.s. I am not sure whose bug - libvirtd or systemd. b.r. Maxim Kozin

> Cool, thanks for the info! Does this still affect libvirt 1.3.2 as well? You > mentioned elsewhere that you weren't hitting this issue with that version Sorry, I miss version and another details. Test make on CentOS Linux release 7.2.1511 (Core) and libvirt 1.3.2, build from sources with next options: --without qemu \ --without xen \ --without openvz \ --without vmware \ --without esx \ --without parallels \ --without bhyve \ --without uml \ --without vbox \ --without selinux \ --with lxc \ --with macvtap \ --without storage-rbd \ --with capng Kernel 3.10.0-327.13.1.el7.x86_64 With version 1.2.18 we had 2 problem - negative value in "used" column and 8Ptb in "total" column. In 1.3.2 "used" columns always show positive values. b.r. Maxim Kozin

Now reporduced with 100% 1) create contrainer with memory limit 1Gb 2) run inside simple memory test allocator: