> -----Original Message----- > From: Elliott, Robert (Persistent Memory) [mailto:elliott at hpe.com] > Sent: Saturday, August 20, 2016 2:58 AM > To: Sreekanth Reddy > Cc: linux-scsi at vger.kernel.org; linux-kernel at vger.kernel.org; > irqbalance at lists.infradead.org; Kashyap Desai; Sathya Prakash Veerichetty; > Chaitra Basappa; Suganath Prabu Subramani > Subject: RE: Observing Softlockup's while running heavy IOs > > > > > -----Original Message----- > > From: Sreekanth Reddy [mailto:sreekanth.reddy at broadcom.com] > > Sent: Friday, August 19, 2016 6:45 AM > > To: Elliott, Robert (Persistent Memory) <elliott at hpe.com> > > Subject: Re: Observing Softlockup's while running heavy IOs > > > ... > > Yes I am also observing that all the interrupts are routed to one CPU. > > But still I observing softlockups (sometime hardlockups) even when I > > set rq_affinity to 2. How about below scenario ? For simplicity. HBA with single MSI-x vector. (Whenever HBA supports less MSI-x and logical CPUs are more on system, we can see chance of these issue frequently..) Assume we have 32 logical CPU (4 socket, each with 8 logical CPU). CPU-0 is not participating in IO. Remaining CPU range from 1 to 31 is submitting IO. In such a scenario rq_affinity=2 and irqbalance supporting *exact* smp_affinity_hint will not help. We may see soft/hard lockup on CPU-0.. Are we going to resolve such issue or it is very rare to happen on field ? > > That'll ensure the block layer's completion handling is done there, but > not your > driver's interrupt handler (which precedes the block layer completion > handling). > > > > Is their any way to route the interrupts the same CPUs which has > > submitted the corresponding IOs? > > or > > Is their any way/option in the irqbalance/kernel which can route > > interrupts to CPUs (enabled in affinity_hint) in round robin manner > > after specific time period. > > Ensure your driver creates one MSIX interrupt per CPU core, uses that > interrupt > for all submissions from that core, and reports that it would like that > interrupt to > be serviced by that core in /proc/irq/nnn/affinity_hint. > > Even with hyperthreading, this needs to be based on the logical CPU cores, > not > just the physical core or the physical socket. > You can swamp a logical CPU core as easily as a physical CPU core. > > Then, provide an irqbalance policy script that honors the affinity_hint > for your > driver, or turn off irqbalance and manually set /proc/irq/nnn/smp_affinity > to > match the affinity_hint. > > Some versions of irqbalance honor the hints; some purposely don't and need > to > be overridden with a policy script. > > > --- > Robert Elliott, HPE Persistent Memory >
