On Wed, Mar 07, 2018 at 10:58:34PM +0530, Kashyap Desai wrote: > > > > > > Also one observation using V3 series patch. I am seeing below Affinity > > > mapping whereas I have only 72 logical CPUs. It means we are really > > > not going to use all reply queues. > > > e.a If I bind fio jobs on CPU 18-20, I am seeing only one reply queue > > > is used and that may lead to performance drop as well. > > > > If the mapping is in such shape, I guess it should be quite difficult to > figure out > > one perfect way to solve this situation because one reply queue has to > handle > > IOs submitted from 4~5 CPUs at average. > > 4.15.0-rc1 kernel has below mapping - I am not sure which commit id in " > linux_4.16-rc-host-tags-v3.2" is changing the mapping of IRQ to CPU. It I guess the mapping you posted is read from /proc/irq/126/smp_affinity. If yes, no any patch in linux_4.16-rc-host-tags-v3.2 should change IRQ affinity code, which is done in irq_create_affinity_masks(), as you saw, no any patch in linux_4.16-rc-host-tags-v3.2 touches that code. Could you simply apply the patches in linux_4.16-rc-host-tags-v3.2 against 4.15-rc1 kernel and see any difference? > will be really good if we can fall back to below mapping once again. > Current repo linux_4.16-rc-host-tags-v3.2 is giving lots of random mapping > of CPU - MSIx. And that will be problematic in performance run. > > As I posted earlier, latest repo will only allow us to use *18* reply Looks not see this report before, could you share us how you conclude that? The only patch changing reply queue is the following one: https://marc.info/?l=linux-block&m=151972611911593&w=2 But not see any issue in this patch yet, can you recover to 72 reply queues after reverting the patch in above link? > queue instead of *72*. Lots of performance related issue can be pop up on > different setup due to inconsistency in CPU - MSIx mapping. BTW, changes > in this area is intentional @" linux_4.16-rc-host-tags-v3.2". ? As you mentioned in the following link, you didn't see big performance drop with linux_4.16-rc-host-tags-v3.2, right? https://marc.info/?l=linux-block&m=151982993810092&w=2 Thanks, Ming
