Re: [PATCH 0/3] timer: Improve itimers scalability

Steven Rostedt
2015-08-27T14:47:13Z

On Thu, 27 Aug 2015 15:18:49 +0200
Frederic Weisbecker <fweisbec@gmail.com> wrote:

> On Wed, Aug 26, 2015 at 04:45:44PM -0700, Hideaki Kimura wrote:
> > I totally agree that this is not a perfect solution. If there are 10x more
> > cores and sockets, just the atomic fetch_add might be too expensive.
> >
> > However, it's comparatively/realistically the best thing we can do without
> > any drawbacks. We can't magically force all library developers to write the
> > most scalable code always.
> >
> > My point is: this is a safety net, and a very effective one.
>
> I mean the problem here is that a library uses an unscalable profiling feature,
> unconditionally as soon as you load it without even initializing anything. And
> this library is used in production.
>
> At first sight, fixing that in the kernel is only a hack that just reduces a bit
> the symptoms.
>
> What is the technical issue that prevents from fixing that in the library itself?
> Posix timers can be attached anytime.

I'm curious to what the downside of this patch set is? If we can fix a
problem that should be fixed in userspace, but does not harm the kernel
by doing so, is that bad? (an argument for kdbus? ;-)

As Hideaki noted, this could be a problem in other locations as well
that people have yet to find.

-- Steve