Re: [Lse-tech] Proposal for Enhanced Accounting HOWTO

[Jay L. <jl...@sg...>]

I think Andrew removed pagg for lack of code that uses pagg?
I added Andrew to cc on this.

Pagg has completed code review cycle. I am not concerned of this.
The users of pagg are trying to get accepted :)  CSA is one user
of pagg and we have other software that needs pagg is working on
release under GPL license.

Thanks,
  - jay


Guillaume Thouvenin wrote:
>                        Enhanced Accounting HOWTO
> 		       =========================
>  
>   According to discussion on the lse-tech mailing-list, it appears that
> three steps (at least) are required to improve accounting. 
> 
> 1) Improve accounting structure
>    ----------------------------
> 
>    The current BSD-accounting structure doesn't have enough informations. 
> Metrics computed by CSA module can be added to BSD accounting. According 
> to other discussion (like Andi Kleen's comment on the patch I wrote when 
> I wanted to add CSA IO values in the BSD accounting 
> ( http://lkml.org/lkml/2004/8/2/70 ) the current method to get metrics 
> about blocks/char read/write is not accurate since most writes can be 
> accounted by some pdflush threads. Maybe add a counter in the routine
> mpage_writepages() but I don't know if we can recover a process ID from 
> the struct page and I don't know if it will be enough... I'm looking if 
> this is the right way.
> 
> 
> 2) Group of processes management
>    ------------------------------
> 
>    We need to be able to manage groups of processes as it's clear that 
> a major accounting improvement is the per-job accounting. I don't know if 
> "job" is the right noun. There are several implementation that already exist
> and some of them are already in the kernel. The property needed here is that 
> if a process is in a container, its children will be in the same container. 
> Different implementations can be:
> 
> 	- PAGG + JOB (job)
> 	- ELSA (bank)
> 	- CKRM (class)
> 	- CPUSET (a cpuset of all CPUs can act as a container)
> 
>    The interface between kernel and user space application can be a new virtual
> file system (like CKRM does with /rcfs) but it can also be a device driver with
> ioctl operations (like ELSA does). Both solutions are interesting and need to
> be discussed. We can notice that CPUSET is in 2.6.9-rc1-mm2 tree and it seems 
> that PAGG has been removed (don't know why) from -mm tree.
>    
> 3) Data presentation
>    -----------------
> 	
>     We can have several different implementations. 
> 
> 4) General overview
>    ----------------
> 
>           KERNEL SPACE        |   USER SPACE (or MODULE)       	     
> 	                      |
>          ----------------     | 
>         | BSD accounting |    | 
> 	|       +        |    |     ------------
>         |      CSA       |<=======>|            |
>          ----------------     |    |  Enhanced  |
>                               |    | Accounting |
>             -------------     |    |    Core    |
>            |  group of   |<=======>|            |
>            |  processes  |    |     ------------
>            |  manager    |    |
>             -------------     |
>                               |
> 			       
>   Communication between EAC (Enhanced Accounting Core) and kernel space can be
> done via virtual fs or a device. The goal of EAC is to keep a trace of the
> different groups of processes during the accounting period using the group of
> processes management module. The idea is that the group of processes management
> can send a message to EAC when a process ended to indicate the job
> ID if any. The other thing that has to be done by EAC is the data presentation.
> 
>   Here is an example of what can be done:
> 
>   1) First we can add processes into containers using the GPM (group of 
>      processes manager) module. For example we can add an ftp server with 
>      pid #123 and a daemon ssh with pid #234. Thus, inside the GPM you have:
>          container 1 -> 123
> 	 container 2 -> 234
> 
>   2) Now, a user can login via ssh, so, sshd will create new children. Thus, 
>      inside the GPM you will have something like:
>          container 1 -> 123
> 	 container 2 -> 234 333 334 335
> 
>   3) As soon as a process is terminated, the EAC must be aware of that fact 
>      (using a signal from GPM for example). There is just this modification
>      that is needed. With the signal, the GPM will transfer information like
>      pid, jib (job ID), command, ... to the EAC. This will allow to keep trace
>      about what happens in the system. Thus, in the EAC we keep information 
>      about all processes that are finished. 
> 
>   4) If the sysadmin asks information about process 234, the EAC will know that
>      it belongs to container 2 and there are other processes in this container.
>      As all processes are exited, accounting information are written in the 
>      accounting file (like it is currently with BSD accounting). With those 
>      informations (accounting + job information) we can do per-job accounting.
> 
>   I am working on the EAC implementation to check how we can make it work.
> 
> Any comments?
> 
> Best
> Guillaume
> 
> 
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