Re: [ckrm-tech] RFC: Memory Controller
From: Paul Menage
Date: Tue Oct 31 2006 - 12:23:01 EST
On 10/31/06, Balbir Singh <balbir@xxxxxxxxxx> wrote:
I am still a little concerned about how limit size changes will be implemented.
Will the cpuset "mems" field change to reflect the changed limits?
That's how we've been doing it - increasing limits is easy, shrinking
them is harder ...
> Page cache control is actually more essential that RSS control, in our
> experience - it's pretty easy to track RSS values from userspace, and
> react reasonably quickly to kill things that go over their limit, but
> determining page cache usage (i.e. determining which job on the system
> is flooding the page cache with dirty buffers) is pretty much
> impossible currently.
>
Hmm... interesting. Why do you think its impossible, what are the kinds of
issues you've run into?
Issues such as:
- determining from userspace how much of the page cache is really
"free" memory that can be given out to new jobs without impacting the
performance of existing jobs
- determining which job on the system is flooding the page cache with
dirty buffers
- accounting the active pagecache usage of a job as part of its memory
footprint (if a process is only 1MB large but is seeking randomly
through a 1GB file, treating it as only using/needing 1MB isn't
practical).
Paul
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