KSM only works with applications which support it:
KSM only operates on those areas of address space which an application has
advised to be likely candidates
for merging, by using the madvise(2) system call: int madvise(addr,
length, MADV_MERGEABLE.
This means that doing:
echo 1 > /sys/kernel/mm/ksm/run
will be enough for KVM, but will not do anything for applications like bash,
nginx, apache, php-fpm and so on.
Please refer to "Enabling memory deduplication libraries in containers" on
https://openvz.org/KSM_(kernel_same-page_merging) - you will have to use
ksm_preload mentioned. I haven't personally used it with LXD.
Tomasz Chmielewski
https://lxadm.com
On Monday, June 05, 2017 09:48 JST, Ron Kelley <[email protected]> wrote:
> Thanks Fajar.
>
> This is on-site with our own physical servers, storage, etc. The goal is to
> get the most containers per server as possible. While our servers have lots
> of RAM, we need to come up with a long-term scaling plan and hope KSM can
> help us scale beyond the standard numbers.
>
> As for the openvz link; I read that a few times but I don’t get any positive
> results using those methods. This leads me to believe (a) LXD does not
> support KSM or (b) the applications are not registering w/the KSM part of the
> kernel.
>
> I am going to run through some tests this week to see if I can get KSM
> working outside the LXD environment then try to replicate the same tests
> inside LXD.
>
> Thanks again for the feedback.
>
>
>
> > On Jun 4, 2017, at 6:15 PM, Fajar A. Nugraha <[email protected]> wrote:
> >
> > On Sun, Jun 4, 2017 at 11:16 PM, Ron Kelley <[email protected]> wrote:
> > (Reviving the thread about Container Scaling:
> > https://lists.linuxcontainers.org/pipermail/lxc-users/2016-May/011607.html)
> >
> > We have hit critical mass with LXD 2.12 and I need to get Kernel Samepage
> > Merging (KSM) working as soon as possible. All my research has come to a
> > dead-end, and I am reaching out to the group at large for suggestions.
> >
> > Background: We have 5 host servers - each running U16.04
> > (4.4.0-57-generic), 8G RAM, 20G SWAP, and 50 containers (exact configs per
> > server - nginx and php 7).
> >
> >
> > Is this a cloud, or on-site setup?
> >
> > For cloud, there are a lot of options that could get you running with MUCH
> > more memory, which would save you lots of headaches getting KSM to work. My
> > favorite is EC2 spot instance on AWS.
> >
> > On another note, I now setup most of my hosts with no swap, since
> > performance plummets whenever swap is used. YMMV.
> >
> >
> > I am trying to get KSM working since each container is an identical replica
> > of the other (other than hostname/IP). I have read a ton of information on
> > the ‘net about Ubuntu and KSM, yet I can’t seem to get any pages to share
> > on the host. I am not sure if this is a KSM config issue or if LXD won’t
> > allow KSM between containers.
> >
> >
> >
> >
> >
> > Here is what I have done thus far:
> > ----------------------------------
> > * Installed the ksmtuned utility and verified ksmd is running on each host.
> > * Created the ksm_preload and ksm-wrapper tools per this site (the
> > https://github.com/unbrice/ksm_preload).
> > * Created 50 identical Ubuntu 16.04 containers running nginx
> > * Modified the nginx startup script on each container to include the
> > ksm_preload.so library; no issues running nginx.
> >
> > (Note: since I could not find the ksm_preload library for Ubuntu, I had to
> > use the ksm-wrapper tool listed above)
> >
> > All the relevant files under /sys/kernel/mm/ksm still show 0 (pages_shared,
> > pages_sharing, etc) regardless of what I do.
> >
> >
> > Can any (@stgraber @brauner) confirm if KSM is supported with LXD? If so,
> > what is the “magic” to make it work? We really want to get 2-3x more sites
> > per container if possible.
> >
> >
> > Have you read https://openvz.org/KSM_(kernel_same-page_merging) ? Some info
> > might be relevant. For example, it mentions something which you did not
> > wrote:
> >
> > To start ksmd, issue
> > [root@HN ~]# echo 1 > /sys/kernel/mm/ksm/run
> >
> > Also the section about Tuning and Caveats.
> >
> > --
> > Fajar
> > _______________________________________________
> > lxc-users mailing list
> > [email protected]
> > http://lists.linuxcontainers.org/listinfo/lxc-users
>
> _______________________________________________
> lxc-users mailing list
> [email protected]
> http://lists.linuxcontainers.org/listinfo/lxc-users
--
Tomasz Chmielewski
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