Re: [patch 2/3] scheduler: add full memory barriers upon taskswitch at runqueue lock/unlock

[Steven Rostedt]

On Tue, 2010-02-02 at 01:58 +1100, Nick Piggin wrote:
> On Mon, Feb 01, 2010 at 09:47:59AM -0500, Mathieu Desnoyers wrote:
> > * Nick Piggin (npiggin@xxxxxxx) wrote:
> > > Well I just mean that it's something for -rt to work out. Apps can
> > > still work if the call is unsupported completely.
> > 
> > OK, so we seem to be settling for the spinlock-based sys_membarrier()
> > this time, which is much less intrusive in terms of scheduler
> > fast path modification, but adds more system overhead each time
> > sys_membarrier() is called. This trade-off makes sense to me, as we
> > expect the scheduler to execute _much_ more often than sys_membarrier().
> > 
> > When I get confirmation that's the route to follow from both of you,
> > I'll go back to the spinlock-based scheme for v9.
> 
> I think locking or cacheline bouncing DoS is just something we can't
> realistically worry too much about in the standard kernel. No further
> than just generally good practice of good scalability, avoiding
> starvations and long lock hold times etc.
> 
> So I would prefer the simpler version that doesn't add overhead to
> ctxsw, at least for the first implementation.

Acked-by: Steven Rostedt <rostedt@xxxxxxxxxxx>

;-)

-- Steve


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/