On Thu, Jun 4, 2015 at 11:57 AM, George Dunlap <dunlapg at umich.edu> wrote: > On Thu, Jun 4, 2015 at 6:03 AM, Sarah Newman <srn at prgmr.com> wrote: >> By default, /var/lib/xenstored is mounted tmpfs in centos 5 but this doesn't appear to be true for Xen4CentOS. This can cause performance issues as >> mentioned in https://bugzilla.redhat.com/show_bug.cgi?id=446089 >> >> I'm not sure if this should be part of xencommons, but if not, adding a tmpfs mount should probably be documented on the quick start wiki page. > > Sarah, > > Thanks for looking into this. > > Adding a tmpfs mount to xencommons, if using the C xenstored, might be > a good idea -- I'll float that with upstream and see what they say. > > As an alternate, can you try using the ocaml-based oxenstored (which > doesn't use the filesystem as its atomicity mechanism)? > > To use oxenstored: > * Install the xen-ocaml package > * Reboot dom0 > * Verify that oxenstored is running: > # ps ax | grep xenstore > 654 ? S 0:00 /usr/sbin/oxenstored --pid-file > /var/run/xenstored.pid > > (On my to-do list is to get oxenstored into the core xen-runtime > package, which would also resolve this situation, I believe.) FWIW, I used the following shell snippet to create 80 VMs (which crash immediately without an initrd but still take up space in xenstore): for i in {1..80} ; do xl create null.cfg name=\"t$i\" kernel=\"/boot/vmlinuz-3.18.12-11.el7.x86_64\" memory=\"40\" on_crash=\"preserve\" ; done And then used the shell snippet from the bug report to generate load: while true; do xl list &> /dev/null; usleep 5000;done With xenstored normally the CPU load was about 30%. Mounted under tmpfs, it was slightly smaller, around 20%, but swung around wildly. With oxenstored it was about 15%. This is with xfs as the filesystem. That doesn't seem big enough to warrant a lot of effort: if you can reproduce the 75% numbers from the bug report I'll pursue it further, otherwise I'll probably just leave it. -George