linux-kernel - Re: [PATCH] Add hierarchical accounting to cpu accounting controller

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20081031094041.194a32d9.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Fri, 31 Oct 2008 09:40:41 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Dhaval Giani <dhaval@...ux.vnet.ibm.com>
Cc:	Li Zefan <lizf@...fujitsu.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	bharata@...ux.vnet.ibm.com, Paul Menage <menage@...gle.com>,
	linux-kernel@...r.kernel.org,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] Add hierarchical accounting to cpu accounting
 controller

On Thu, 30 Oct 2008 22:46:22 +0530
Dhaval Giani <dhaval@...ux.vnet.ibm.com> wrote:

> On Mon, Oct 27, 2008 at 04:25:01PM +0800, Li Zefan wrote:
> > >>>> 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.
> > > 
> > 
> > cpuacct was designed to count cpu usage of a group of tasks, and now some people
> > want it to also take child group's usage into account, so I think this is a feature
> > request but not a bug fix.
> > 
> 
> I disagree. The child is a part of the parent's hierarchy, and therefore
> its usage should reflect in the parent's usage.
> 

In my point of view, there is no big difference. It's just whether we need a tool
in userland or not. If there is no performance impact, I have no objections.

One request from me is add Documentation/controllers/cpuacct.txt or some to explain
"what we see".

Thanks,
-Kame

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/