On Mon, 2011-09-12 at 09:33 +0200, Thomas Gleixner wrote:

On Sun, 11 Sep 2011, Mike Galbraith wrote:

quoted

I'm very definitely missing sirq threads from the wakeup latency POV.

(Other things are muddying the water, eg. rcu boost, if wired up and
selected always ramming boosted threads through the roof instead of
configured boost prio.. etc etc, but this definitely improves my latency
woes a lot)

This is a giant step backward from "let's improve abysmal throughput",
so I'm wondering if anyone has better ideas.

One of the problems we have are the signal based timers (posix-timer,
itimer).

That's the biggest part of my jitter troubles.

 We really want to move the penalty for those into the context
of the thread/process to which those timers belong. The trick is to
just note the expiry of a timer and wake up the target which has to
deal with the real work in his own context and on his own
account. That's rather simple for thread bound signals, but has a lot
of implications with process wide ones. Though it should be doable and
I'd rather see that solved than hacking around with the split softirqs

That definitely sounds like a better idea.. for someone who thoroughly
understands signals.
 

quoted

WRT below: "fixes" are dinky, this is not...

sched, rt, sirq: resurrect sirq threads for RT_FULL

Not-signed-off-by: Mike Galbraith [off-list ref]

Not-that-delighted: tglx

Ditto.

	-Mike