Re: [RFC PATCH v4 00/13] ktask: multithread CPU-intensive kernel work

Tejun Heo
2018-12-03T16:16:33Z

Hello,

On Fri, Nov 30, 2018 at 04:13:07PM -0800, Daniel Jordan wrote:
> On Fri, Nov 30, 2018 at 11:18:19AM -0800, Tejun Heo wrote:
> > Hello,
> >
> > On Mon, Nov 05, 2018 at 11:55:45AM -0500, Daniel Jordan wrote:
> > > Michal, you mentioned that ktask should be sensitive to CPU utilization[1].
> > > ktask threads now run at the lowest priority on the system to avoid disturbing
> > > busy CPUs (more details in patches 4 and 5). Does this address your concern?
> > > The plan to address your other comments is explained below.
> >
> > Have you tested what kind of impact this has on bandwidth of a system
> > in addition to latency? The thing is while this would make a better
> > use of a system which has idle capacity, it does so by doing more
> > total work. It'd be really interesting to see how this affects
> > bandwidth of a system too.
>
> I guess you mean something like comparing aggregate CPU time across threads to
> the base single thread time for some job or set of jobs? Then no, I haven't
> measured that, but I can for next time.

Yeah, I'm primarily curious how expensive this is on an already loaded
system, so sth like loading up the system with a workload which can
saturate the system and comparing the bw impacts of serial and
parallel page clearings at the same frequency.

Thanks.

--
tejun