From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chetan.Loke@Emulex.Com (Chetan.Loke@Emulex.Com) Date: Wed, 25 Mar 2009 06:52:32 -0700 Subject: [ltt-dev] [patch 3/9] LTTng instrumentation tasklets In-Reply-To: <20090324175621.GE31117@elte.hu> References: <20090324155625.420966314@polymtl.ca> <20090324160148.238795468@polymtl.ca> <20090324175621.GE31117@elte.hu> Message-ID: > -----Original Message----- > From: linux-kernel-owner@vger.kernel.org > [mailto:linux-kernel-owner at vger.kernel.org] On Behalf Of Ingo Molnar > Sent: Tuesday, March 24, 2009 1:56 PM > To: Mathieu Desnoyers > Cc: akpm at linux-foundation.org; linux-kernel at vger.kernel.org; > ltt-dev at lists.casi.polymtl.ca; Frederic Weisbecker; Jason > Baron; Peter Zijlstra; Thomas Gleixner; Russell King; Masami > Hiramatsu; Frank Ch. Eigler; Hideo AOKI; Takashi Nishiie; > Steven Rostedt; Eduard - Gabriel Munteanu > Subject: Re: [patch 3/9] LTTng instrumentation tasklets > > > * Mathieu Desnoyers wrote: > > > tasklet entry and exit events. > > > +DEFINE_TRACE(irq_tasklet_high_entry); > > +DEFINE_TRACE(irq_tasklet_high_exit); > > +DEFINE_TRACE(irq_tasklet_low_entry); > > +DEFINE_TRACE(irq_tasklet_low_exit); > > Dunno - tasklets are a legacy mechanism, not sure we want to > instrument them. 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? thanks Chetan