From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chetan.Loke@Emulex.Com (Chetan.Loke@Emulex.Com) Date: Wed, 25 Mar 2009 10:37:20 -0700 Subject: [ltt-dev] [patch 3/9] LTTng instrumentation tasklets In-Reply-To: <1237990678.7972.1094.camel@twins> References: <20090324155625.420966314@polymtl.ca> <20090324160148.238795468@polymtl.ca> <20090324175621.GE31117@elte.hu> <1237990678.7972.1094.camel@twins> Message-ID: > -----Original Message----- > From: Peter Zijlstra [mailto:peterz@infradead.org] > Sent: Wednesday, March 25, 2009 10:18 AM > To: Loke,Chetan > Cc: mingo at elte.hu; mathieu.desnoyers at polymtl.ca; > akpm at linux-foundation.org; linux-kernel at vger.kernel.org; > ltt-dev at lists.casi.polymtl.ca; fweisbec at gmail.com; > jbaron at redhat.com; tglx at linutronix.de; > rmk+lkml at arm.linux.org.uk; mhiramat at redhat.com; > fche at redhat.com; haoki at redhat.com; > t-nishiie at np.css.fujitsu.com; rostedt at goodmis.org; > eduard.munteanu at linux360.ro > Subject: RE: [patch 3/9] LTTng instrumentation tasklets > > On Wed, 2009-03-25 at 06:52 -0700, Chetan.Loke at 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.