Re: [uml-devel] [patch] fix uml slowness caused by ptrace preemption bug on host

2009-03-20 Thread Oleg Nesterov
On 03/20, Miklos Szeredi wrote: > > I'm no scheduler expert either. neither me ;) > --- linux.git.orig/kernel/sched.c 2009-03-18 12:53:47.0 +0100 > +++ linux.git/kernel/sched.c 2009-03-20 08:58:13.0 +0100 > @@ -4629,7 +4629,8 @@ asmlinkage void __sched preempt_schedule >

Re: [uml-devel] [patch] fix uml slowness caused by ptrace preemption bug on host

2009-03-20 Thread Miklos Szeredi
On Thu, 19 Mar 2009, Roland McGrath wrote: > I'm no scheduler expert and I don't know whether the exact placement in > your change is the optimal one. But it's certainly fine from a ptrace > perspective. I'm no scheduler expert either. Maybe a more generic solution in the scheduler (something li

Re: [uml-devel] [patch] fix uml slowness caused by ptrace preemption bug on host

2009-03-20 Thread Oleg Nesterov
On 03/19, Roland McGrath wrote: > > I'm no scheduler expert and I don't know whether the exact placement in > your change is the optimal one. Agreed, can't we do a bit more simple patch? --- kernel/signal.c +++ kernel/signal.c @@ -1572,8 +1572,10 @@ static void ptrace_stop

Re: [uml-devel] [patch] fix uml slowness caused by ptrace preemption bug on host

2009-03-20 Thread Ingo Molnar
* Miklos Szeredi wrote: > On Fri, 20 Mar 2009, Peter Zijlstra wrote: > > On Thu, 2009-03-19 at 23:23 +0100, Miklos Szeredi wrote: > > > > > > This patch solves this by not scheduling on preempt_enable() after > > > ptrace_stop() has woken up the tracer. > > > > Nice,.. however did you find thi

Re: [uml-devel] [patch] fix uml slowness caused by ptrace preemption bug on host

2009-03-20 Thread Miklos Szeredi
On Fri, 20 Mar 2009, Peter Zijlstra wrote: > On Thu, 2009-03-19 at 23:23 +0100, Miklos Szeredi wrote: > > > > This patch solves this by not scheduling on preempt_enable() after > > ptrace_stop() has woken up the tracer. > > Nice,.. however did you find this? Ftrace helped a lot, it's a really co

Re: [uml-devel] [patch] fix uml slowness caused by ptrace preemption bug on host

2009-03-20 Thread Peter Zijlstra
On Thu, 2009-03-19 at 23:23 +0100, Miklos Szeredi wrote: > From: Miklos Szeredi > > This patch fixes bug #12208. > > This turned out to be not a scheduler regression, but an already > existing problem in ptrace being triggered by subtle scheduler > changes. > > The problem is this: > > - task

Re: [uml-devel] [patch] fix uml slowness caused by ptrace preemption bug on host

2009-03-19 Thread Roland McGrath
I'm no scheduler expert and I don't know whether the exact placement in your change is the optimal one. But it's certainly fine from a ptrace perspective. Thanks, Roland -- Apps built with the Adobe(R) Flex(R) framework