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Re: [Xen-devel] Re: [PATCH 7/9] blkio-cgroup-v9: Page tracking hooks

On Fri, 24 Jul 2009 14:44:16 +0900 (JST)
Ryo Tsuruta <ryov@xxxxxxxxxxxxx> wrote:
 good solution to resolve such problem.
> > My point is "don't allow anyone to use bandwidth of others."
> > Considering job isolation, a thread who requests swap-out should be charg=
> > ed
> > against bandwidth.
> From another perspective, the swap-out is caused since the buggy
> process uses a large amount of memory, so it can be considered as 
> the bandwidth of logging process is used due to the buggy process.
> Please consider the following case. If a thread who requests swap-out
> is charged, the thread is charged other threads' I/O.
>    (1)                          --------      (2)
>    Process A                   |        |     Process B
>    mmaps a large area in   --> | memory | <-- tries to allocate a page.
>    the memory and writes       |        |
>    data to there.               --------     (3)
>                                    |         To get a free page,
>                                    |         the data written by Proc.A
>                                    |         is written out to the disk.
>                                    V         The I/O is done by using
>                                 ---------    Proc.B's bandwidth.
>                                |  disk   |   
>                                 ---------
> Thus I think that page owners should be charged against bandwidth.
Ok, no good way. yours is wrong, mine is wrong, too.
plz find 3rd way, reasonable.

Below is brief thinking.

"Why process A should be charged to I/O when it just maps anon memory ?"
I can't answer this.

Even in yorr case, Process B requests memory and get penalty. It's
very natural, I think.

In usual case, 
 - if process A maps ANON, there will be no I/O.
 - if process A maps FILE, it will be charged to process A.
ok ?

Under memory pressure,
 - if process A maps ANON, swap I/O should be charged to process B.
 - if process A maps FILE, I/O should be charged to process A.

Anyway, there will be ineraction with dirty_ratio of memcg (not implemeted yet)
and _Owner should be charged_ issue will be handled in this dirty_ratio layer.
More consideration is necessary, I think.


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