Re: [RFC][PATCH 4/7] UBC: syscalls (user interface)

Rohit Seth
2006-08-17T17:09:44Z

On Thu, 2006-08-17 at 16:13 +0400, Kirill Korotaev wrote:
> Rohit Seth wrote:
> > On Wed, 2006-08-16 at 20:04 +0100, Alan Cox wrote:
> >
> >>Ar Mer, 2006-08-16 am 11:17 -0700, ysgrifennodd Rohit Seth:
> >>
> >>>I think there should be a check here for seeing if the new limits are
> >>>lower than the current usage of a resource. If so then take appropriate
> >>>action.
> >>
> >>Generally speaking there isn't a sane appropriate action because the
> >>resources can't just be yanked.
> >>
> >
> >
> > I was more thinking about (for example) user land physical memory limit
> > for that bean counter. If the limits are going down, then the system
> > call should try to flush out page cache pages or swap out anonymous
> > memory. But you are right that it won't be possible in all cases, like
> > for in kernel memory limits.
> Such kind of memory management is less efficient than the one
> making decisions based on global shortages and global LRU alogrithm.
>
> The problem here is that doing swap out takes more expensive disk I/O
> influencing other users.
>
> So throttling algorithms if wanted should be optional, not mandatory.
> Lets postpone it and concentrate on the core.
>

I'm really interested in seeing what changes you make in alloc_page when
the container limits are hit.

When a container is throttling then yes it will have some additional
cost to other containers but that is the cost of sharing an underlying
platform.

-rohit