[systemd-devel] Start-up resource and prioritization control

[Uoti Urpala]

On Tue, 2014-05-20 at 15:16 +0200, Umut Tezduyar Lindskog wrote:
> On Tue, May 20, 2014 at 1:46 PM, Tom Gundersen <teg at jklm.no> wrote:
> > Wouldn't this be solved by telling the kernel to schedule the starting
> > services with high latency (or whatever the terminology is), i.e.,
> > give each of them a relatively large timeslice. That would decrease
> > the flushing, but at the same time avoid any issues with deadlocks
> > etc. It should also give us the flexibility to give some services low
> > latency if that is required for them etc (think udev/systemd/dbus and
> > otherthings which would otherwise block boot).
> 
> This is exactly what the cpu.shares cgroup property does and that is
> what the patch posted on ML is trying to utilize.

I don't think they are the same. If I understood correctly, the patch
was about setting priorities. Latency is a different thing.

Your problem was context switch overhead. That can be fixed by making
the kernel switch tasks less often - even if there are 100 runnable
tasks, if the kernel keeps running each task for a second before
switching to the next one, context switch overhead will not be large.