On Wed, Mar 27, 2013 at 02:28:32PM -0700, Andrew Morton wrote:
> On Mon, 18 Mar 2013 17:44:42 -0400 Andrew Shewmaker <agshew@xxxxxxxxx> wrote:
>
> > Add user_reserve_kbytes knob.
> >
> > Limit the growth of the memory reserved for other user
> > processes to min(3% current process size, user_reserve_pages).
> >
> > user_reserve_pages defaults to min(3% free pages, 128MB)
>
> That was an epic changelog ;)
I didn't want to err on the side of brevity again :)
But I definitely don't want to be annoying, so I'll work
on being concise without sacrificing important detail.
> >
> > ...
> >
> > +int __meminit init_user_reserve(void)
> > +{
> > + unsigned long free_kbytes;
> > +
> > + free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
> > +
> > + sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
> > + return 0;
> > +}
> > +module_init(init_user_reserve)
>
> Problem is, the initial default values will become wrong if memory if
> hot-added or hot-removed.
>
> That could be fixed up by appropriate use of
> register_memory_notifier(), but what would the notification handler do
> if the operator has modified the value? Proportionally scale it?
If the operator changed it to a greater value, then I imagine that would
be because the applications they use to recover require a bigger reserve
to function. Then proportionally scaling down the value on hot-removal
might mean that the operator can't recover when they expected to be able
to. Maybe the best thing would be to leave it be in that case, or
print a message telling them they need to re-evaluate the reserve size?
I won't be able to look at this again until next week, but I'll work on a
version that handles hot-addition and hot-removal.
Thanks,
Andrew
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>