[Devel] Re: [PATCH 4/4] The control group itself

[Pavel Emelyanov]

Paul Menage wrote:
> On Fri, Feb 22, 2008 at 12:12 AM, Pavel Emelyanov <xemul at openvz.org> wrote:
>>  Hmm, you mean make them a binary files?
> 
> No, not by default. But I'm working on a plan to have an optional
> binary API to cgroups, that would allow multiple control files to be
> read in a binary format with a single system call. The existing API
> would still be available as well, of course. The idea would be that
> monitoring programs that frequently read lots of values from a single
> cgroup (or even multiple cgroups) would be able to do so more cheaply
> than by making multiple different reads on different files.
> 
> In order for this to work, CGroups needs to know the data type of a
> given control file - so this would only be available for the control
> files that use typed cgroup output methods rather than the raw file
> output interface.

Sounds reasonable.

>>  I thought that filesystem-based
>>  API should be human readable and writable as much as possible...
>>
> 
> Yes, but even without a binary API it makes sense for values that are
> likely to be parsed by programs be in a consistent format.
> 
> But after thinking more about this, I think that the devices
> permission control file output doesn't really fall under this category
> - from a programmatic point of view, I suspect it's write-only, and
> only humans will be reading the output, for debugging.

Yup. So, if you're fine with the proposed API, I think I will prepare
this set and send it to Andrew this week.

> Paul
> 

Thanks,
Pavel
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