[Devel] Re: [ckrm-tech] [PATCH] BC: resource beancounters (v4) (added user memory)

[Chandra Seetharaman]

On Wed, 2006-09-06 at 17:57 +0400, Kirill Korotaev wrote:
> > On Tue, 2006-09-05 at 19:02 +0400, Kirill Korotaev wrote:
> > 
> >>Core Resource Beancounters (BC) + kernel/user memory control.
> >>
> >>BC allows to account and control consumption
> >>of kernel resources used by group of processes. 
> > 
> > 
> > Hi Kirill, 
> > 
> > I've honestly lost track of these discussions along the way, so I hope
> > you don't mind summarizing a bit.
> I think we need to create wiki to summarize it once and forever.
> http://wiki.openvz.org/UBC_discussion
> 
> > Do these patches help with accounting for anything other than memory?
> this patch set - no, but the complete one - does:
> * numfile
> * numptys
> * numsocks (TCP, other, etc.)
> * numtasks
> * numflocks
> ...
> this list of resources was chosen to make sure that no DoS from the container
> is possible.
> This list is extensible easily and if resource is out of interest than
> its limits can be set to unlimited.
> 
> > Will we need new user/kernel interfaces for cpu, i/o bandwidth, etc...?
> no. no new interfaces are required.

Good to know that. 

Your CPU controller supports guarantee ?

Do you have a i/o controller ?

> 
> BUT: I remind you the talks at OKS/OLS and in previous UBC discussions.
> It was noted that having a separate interfaces for CPU, I/O bandwidth

But, it will be lot simpler for the user to configure/use if they are
together. We should discuss this also.

> and memory maybe worthwhile. BTW, I/O bandwidth already has a separate
> interface :/
> 
> > Have you given any thought to the possibility that a task might need to
> > move between accounting contexts?  That has certainly been a
> > "requirement" pushed on to CKRM for a long time, and the need goes
> > something like this:
> Yes we thought about this and this is no more problematic for BC
> than for CKRM. See my explanation below.
> 
> > 1. A system runs a web server, which services several virtual domains
> > 2. that web server receives a request for foo.com
> > 3. the web server switches into foo.com's accounting context
> > 4. the web server reads things from disk, allocates some memory, and
> >    makes a database request.
> > 5. the database receives the request, and switches into foo.com's
> >    accounting context, and charges foo.com for its resource use
> > etc...
> The question is - whether web server is multithreaded or not...
> If it is not - then no problem here, you can change current
> context and new resources will be charged accordingly.
> 
> And current BC code is _able_ to handle it with _minor_ changes.
> (One just need to save bc not on mm struct, but rather on vma struct
> and change mm->bc on set_bc_id()).
> 
> However, no one (can some one from CKRM team please?) explained so far
> what to do with threads. Consider the following example.
> 
> 1. Threaded web server spawns a child to serve a client.
> 2. child thread touches some pages and they are charged to child BC
>    (which differs from parent's one)
> 3. child exits, but since its mm is shared with parent, these pages
>    stay mapped and charged to child BC.
> 
> So the question is:  what to do with these pages?
> - should we recharge them to another BC?
> - leave them charged?

Leave them charged. It will be charged to the appropriate UBC when they
touch it again.

> 
> > So, the goal is to run _one_ copy of an application on a system, but
> > account for its resources in a much more fine-grained way than at the
> > application level.
> Yes.
> 
> > I think we can probably use beancounters for this, if we do not worry
> > about migrating _existing_ charges when we change accounting context.
> > Does that make sense?
> exactly. thats what I'm saying. we can use beancounters for this
> if charges are kept for creator.
> 
> Thanks,
> Kirill
> 
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    Chandra Seetharaman               | Be careful what you choose....
              - sekharan at us.ibm.com   |      .......you may get it.
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