Messages in this thread | | | Date | Mon, 27 Oct 2008 12:27:44 +0530 | From | "Balbir Singh" <> | Subject | Re: [PATCH] Add hierarchical accounting to cpu accounting controller |
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On Mon, Oct 27, 2008 at 10:13 AM, Bharata B Rao <bharata@linux.vnet.ibm.com> wrote: > On Mon, Oct 27, 2008 at 10:17:03AM +0900, KAMEZAWA Hiroyuki wrote: >> On Sat, 25 Oct 2008 08:38:52 -0700 >> "Paul Menage" <menage@google.com> wrote: >> >> > On Fri, Oct 24, 2008 at 11:01 PM, Bharata B Rao >> > <bharata@linux.vnet.ibm.com> wrote: >> > > >> > > Reported-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> >> > > Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com> >> > >> > Reviewed-by: Paul Menage <menage@google.com> > > Thanks Paul. > >> > >> > So in technical terms this patch looks fine now. There's still the >> > question of whether it's OK to change the existing API, since it's >> > been in the kernel in its currently (non-hierarchical) form for >> > several releases now. > > Hmm... Can we consider this as an API change ? Currently cpuacct.usage > readers of a parent accounting group are missing the usage contributions > from its children groups. I would consider this patch as fixing the > above problem by correctly reflecting the cpu usage for every accounting > group. >
If a particular application desires to derive the usage of its immediate tasks and does not care about subcgroups, it is a simple iteration (after this fix)
cpuacct - sigma(cpuacct_child)
and currently if we cared about child accounting, we could do
cpuacct + recursively(sigma(cpuacct_child))
In that sense this fix makes more sense, but like Paul said we need to figure out if it is an API change. My take is that it is a BUG fix, since we do care about child subgroups in accounting.
>> > >> Hmm..how about having 2 params as "aggregated usage" and "private usage" ? >> >> cpuacct.usage. >> cpuacct.all_subtree_usage. > > Is there really a need to differentiate between aggregated and private > usage other than to maintain the current behaviour ? >
That might be useful to have, but as above it can always be derived.
Balbir
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