RE: [patch 3/9] LTTng instrumentation tasklets

[Steven Rostedt]

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

>  
> 
> > -----Original Message-----
> > From: Peter Zijlstra [mailto:peterz@xxxxxxxxxxxxx] 
> > Sent: Wednesday, March 25, 2009 10:18 AM
> > To: Loke,Chetan
> > Cc: mingo@xxxxxxx; mathieu.desnoyers@xxxxxxxxxx; 
> > akpm@xxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; 
> > ltt-dev@xxxxxxxxxxxxxxxxxxxxx; fweisbec@xxxxxxxxx; 
> > jbaron@xxxxxxxxxx; tglx@xxxxxxxxxxxxx; 
> > rmk+lkml@xxxxxxxxxxxxxxxx; mhiramat@xxxxxxxxxx; 
> > fche@xxxxxxxxxx; haoki@xxxxxxxxxx; 
> > t-nishiie@xxxxxxxxxxxxxxxxxx; rostedt@xxxxxxxxxxx; 
> > eduard.munteanu@xxxxxxxxxxx
> > Subject: RE: [patch 3/9] LTTng instrumentation tasklets
> > 
> > On Wed, 2009-03-25 at 06:52 -0700, Chetan.Loke@xxxxxxxxxx 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

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