Re: kdbus: to merge or not to merge?

Andy Lutomirski
2015-08-07T15:09:54Z

On Fri, Aug 7, 2015 at 7:40 AM, Daniel Mack <daniel@zonque.org> wrote:
> On 08/06/2015 08:43 PM, Andy Lutomirski wrote:
>> Nonetheless, it looks like the slice logic (aside: it looks *way* more
>> complicated than necessary -- what's wrong with circular buffers)
>> will, under most (but not all!) workloads, concentrate access to a
>> smallish fraction of the pool. This is IMO bad, since it means that
>> most of the time most of the pool will remain uncommitted. If, at
>> some point, something causes the access pattern to change and hit all
>> the pages (even just once), suddenly all of the pools get committed,
>> and your memory usage blows up.
>
> That's a general problem with memory overcommitment, and not specific to
> kdbus. IOW: You'd have the same problem with a similar logic implemented
> in userspace, right?
>

Sure, except that, if it's in userspace and it starts causing
problems, then userspace can fix it without running into kernel ABI
stability issues.

--Andy