RE: [patch 3/9] LTTng instrumentation tasklets

Steven Rostedt
2009-03-25T17:52:46Z

On Wed, 25 Mar 2009, Chetan.Loke@Emulex.Com wrote:

>
>
> > -----Original Message-----
> > From: Peter Zijlstra [mailto:peterz@infradead.org]
> > Sent: Wednesday, March 25, 2009 10:18 AM
> > To: Loke,Chetan
> > Cc: mingo@elte.hu; mathieu.desnoyers@polymtl.ca;
> > akpm@linux-foundation.org; linux-kernel@vger.kernel.org;
> > ltt-dev@lists.casi.polymtl.ca; fweisbec@gmail.com;
> > jbaron@redhat.com; tglx@linutronix.de;
> > rmk+lkml@arm.linux.org.uk; mhiramat@redhat.com;
> > fche@redhat.com; haoki@redhat.com;
> > t-nishiie@np.css.fujitsu.com; rostedt@goodmis.org;
> > eduard.munteanu@linux360.ro
> > Subject: RE: [patch 3/9] LTTng instrumentation tasklets
> >
> > On Wed, 2009-03-25 at 06:52 -0700, Chetan.Loke@Emulex.Com wrote:
> > > Quick question. I understand this is unrelated to this patch. So I
> > > apologize in advance.
> > > Ingo - you mentioned "tasklets are a legacy mechanism". Is there a
> > > plan to phase them out ? Let me draw a small picture as to what's
> > > bothering me.
> > >
> > > With the SR-IOV support if there are 'N' virtual functions
> > then there
> > > will be 'N' driver instances(actually N+1, 1 for the PF). If that
> > > driver drains the responses in the interrupt context then all such
> > > VF-instances could virtually block everyone else(because
> > SR-IOV guys
> > > might also have MSI-X enabled).
> > > So now all such drivers should alter their Rx path.Driver's
> > can queue
> > > tasklets and can also get the performance they want.
> > >
> > > Any suggestions?
> >
> > Threaded interrupts?
> >
>
> If we truly need to address performance and scalability for the SCSI-subsystem then we need something lightweight.

Threaded interrupts are actually quite light.

-- Steve