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SubjectRe: [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@valinux.co.jp> 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.
maybe.


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.


Bye,
-Kame




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