Hi Stéphane, On Wed, Nov 20, 2013 at 02:23:59PM -0500, Stéphane Graber wrote: > This morning at vUDS we discussed adding support for cgroups in Upstart. > > Before I go into details about the proposed stanza and overall > behaviour, I'd begin by saying that contrary to some other init systems, > our intent is solely related to resource controls which is the main goal > of cgroups. Process grouping and tracking will remain unaffected by the > addition of cgroup support. > > Cgroup support will be implemented by adding a new "cgroup" stanza which > will control the application of cgroup based restrictions to the job. > The limits will be applied to any of the scripts > (pre-start/post-start/job/pre-stop/post-stob) similar to what's done > with setuid/setgid/apparmor stanzas. > > Now my recommended format for the stanza, which I believe should be > flexible enough is: > cgroup <controller> <cgroup name|auto> [<key> <value>] > > > Detail on the fields: > == controller == > Name for one of the cgroup controller > > Currently the valid values are (but won't be hardcoded into upstart): > - blkio > - cpu > - cpuacct > - cpuset > - devices > - freezer > - hugetlb > - memory > - perf_event > > == cgroup-name|$auto == > Name of the cgroup to use (and create if non-existing) > > The name may contain a / (e.g. "db/pgsql" or "db/$auto") indicating that > it's requesting a sub-cgroup. > > "$auto" is the recommended name and will have upstart generate a name > based on the job instance name. > > The main use of that field is for cases where a set of jobs should share > limits, in such case the main job should declare the various values and > the others just refer to the cgroup by name but not defined values. > > The name may be different for the various controllers but may not differ > within the same controller. Example: > valid => cgroup memory group1 limit_in_bytes 52428800 > cgroup cpuset group2 cpus 0-1 > > invalid => cgroup memory group1 limit_in_bytes 52428800 > cgroup memory group1 soft_limit_in_bytes 1024 > > == key == > The cgroup control file minus the controller name, so for example > memory.soft_limit_in_bytes will become limit_in_bytes.
FWIW, typo here as well, this should of course be 'soft_limit_in_bytes' in both cases. > == value == > Any value valid for the given control file, upstart itself won't perform > any validation. > If the value contains spaces, it should be put between double-quotes (e.g.): > cgroup devices auto allow "c 1:2 rwm" > Upstart won't have any controller aware logic in its code, instead, > it'll simply talk over dbus (using a private dbus socket) to the cgroup > manager which will take care of applying the various limits. > That cgroup manager will be started very early in the boot sequence. Any > job containing a cgroup stanza will be held until the manager is > started. > The cgroup will be destroyed when a job is stopped and the cgroup isn't > shared with another job (task count is 0 and it has no child cgroup). Is upstart responsible for destroying the cgroup, or is this done by the cgroup manager? > All of the above is also meant to apply to user sessions. The cgroup > manager will allow unprivileged cgroup configuration, so as long as the > user has write access to a sub-section of a controller, it'll be allowed > to write entries there. Similarly to other restriction stanzas, failure > to apply a cgroup limit in a user session won't be fatal. Seems to leave open the question of how users are given access to the subsection. From what we discussed in the UDS session, I believe we expect logind to set this up for us, correct? Also, the implicit corollary to "cgroup limit failures in a user session aren't fatal" is that, in a system job, they *are* fatal. I know you know this, but it should be documented explicitly. :) Do you intend this writeup to live under http://upstart.ubuntu.com/wiki/ for reference? Thanks, -- Steve Langasek Give me a lever long enough and a Free OS Debian Developer to set it on, and I can move the world. Ubuntu Developer http://www.debian.org/ [email protected] [email protected]
signature.asc
Description: Digital signature
-- upstart-devel mailing list [email protected] Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/upstart-devel
