Re: [PATCH 0/3] fix interrupt swamp in NVMe

[Keith Busch]

On Wed, Aug 21, 2019 at 7:34 PM Ming Lei <ming.lei@xxxxxxxxxx> wrote:
> On Wed, Aug 21, 2019 at 04:27:00PM +0000, Long Li wrote:
> > Here is the command to benchmark it:
> >
> > fio --bs=4k --ioengine=libaio --iodepth=128 --filename=/dev/nvme0n1:/dev/nvme1n1:/dev/nvme2n1:/dev/nvme3n1:/dev/nvme4n1:/dev/nvme5n1:/dev/nvme6n1:/dev/nvme7n1:/dev/nvme8n1:/dev/nvme9n1 --direct=1 --runtime=120 --numjobs=80 --rw=randread --name=test --group_reporting --gtod_reduce=1
> >
>
> I can reproduce the issue on one machine(96 cores) with 4 NVMes(32 queues), so
> each queue is served on 3 CPUs.
>
> IOPS drops > 20% when 'use_threaded_interrupts' is enabled. From fio log, CPU
> context switch is increased a lot.

Interestingly use_threaded_interrupts shows a marginal improvement on
my machine with the same fio profile. It was only 5 NVMes, but they've
one queue per-cpu on 112 cores.