On Fri, Mar 09, 2018 at 11:08:54AM +0100, Thomas Gleixner wrote: > On Fri, 9 Mar 2018, Ming Lei wrote: > > On Fri, Mar 09, 2018 at 12:20:09AM +0100, Thomas Gleixner wrote: > > > On Thu, 8 Mar 2018, Ming Lei wrote: > > > > Actually, it isn't a real fix, the real one is in the following two: > > > > > > > > 0c20244d458e scsi: megaraid_sas: fix selection of reply queue > > > > ed6d043be8cd scsi: hpsa: fix selection of reply queue > > > > > > Where are these commits? Neither Linus tree not -next know anything about > > > them.... > > > > Both aren't merged yet, but they should land V4.16, IMO. > > > > > > > > > This patchset can't guarantee that all IRQ vectors are assigned by one > > > > online CPU, for example, in a quad-socket system, if only one processor > > > > is present, then some of vectors are still assigned by all offline CPUs, > > > > and it is a valid case, but still may cause io hang if drivers(hpsa, > > > > megaraid_sas) select reply queue in current way. > > > > > > So my understanding is that these irq patches are enhancements and not bug > > > fixes. I'll queue them for 4.17 then. > > > > Wrt. this IO hang issue, these patches shouldn't be bug fix, but they may > > fix performance regression[1] for some systems caused by 84676c1f21 ("genirq/affinity: > > assign vectors to all possible CPUs"). > > > > [1] https://marc.info/?l=linux-block&m=152050347831149&w=2 > > Hmm. The patches are rather large for urgent and evtl. backporting. Is > there a simpler way to address that performance issue? Not thought of a simpler solution. The problem is that number of active msix vector is decreased a lot by commit 84676c1f21. However, if someone wants to backport, this patchset can be applied cleanly, no any conflict. Thanks, Ming