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SubjectRe: [PATCH 0/9] Per-cgroup /proc/stat
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On Wed, 2011-09-14 at 17:04 -0300, Glauber Costa wrote:
> [[ For those getting this twice: I sent it previously to containers
> ml, but I guess it was out. Sending now to a broader audience anyway ]]
>
> Hi,
>
> This patchset is a simple initial proposal for a per-cgroup/container
> display of /proc/stat. The display method is based on Daniel's idea of
> exposing a file that can be bind mounted (Daniel, is that more or less
> what you had in mind?)
>
> To grab the stats themselves, I am (ab)using cpuacct cgroup. percpu counters
> are dropped in favor of normal percpu pointers, so we can easily track
> per-cpu quantities.
>
> In case you guys like this idea, my TODO list would include the removal
> of the show stat code in fs/proc/stat.c altogether, and the displaying
> of some fields I haven't touched yet.
>
> Also, to demonstrate one of the potential ideas for such method, I
> implemented a feature comonly found in hypervisors - steal time - on top
> of it. I arguee that containers can/should also display steal time when
> available. Turns out that due to the fact that we run on the same kernel,
> steal time is quite easy to implement once we have per-container tick
> accounting in place.
>
> Please let me know what you guys think
>
> Glauber Costa (9):
> Remove parent field in cpuacct cgroup
> Make cpuacct fields per cpu variables
> Include nice values in cpuacct
> Include irq and softirq fields in cpuacct
> Include guest fields in cpuacct
> Include idle and iowait fields in cpuacct
> Create cpuacct.proc.stat file
> per-cgroup boot time
> Report steal time for cgroup
>
> kernel/sched.c | 265 +++++++++++++++++++++++++++++++++++++++++++++++++-------
> 1 files changed, 234 insertions(+), 31 deletions(-)

I hate it already.. it just smells of more senseless accounting
overhead.

Guys we should seriously trim back a lot of that code, not grow ever
more and more. The sad fact is that if you build a kernel with
cpu-cgroup support the context switch cost is more than double that of a
kernel without, and then you haven't even started creating cgroups yet.

Also, how doesn't all this duplicate part of cpuacct-cgroup?

/me won't actually look at the patches for a little while longer.


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