Re: [PATCH RFC v1 0/3] aio-poll: improve aio-polling efficiency

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Fri, Jan 23, 2026 at 01:15:04PM -0600, JAEHOON KIM wrote:
> On 1/19/2026 12:16 PM, Stefan Hajnoczi wrote:
> > On Tue, Jan 13, 2026 at 11:48:21AM -0600, Jaehoon Kim wrote:
> > > We evaluated the patches on an s390x host with a single guest using 16
> > > virtio block devices backed by FCP multipath devices in a separate-disk
> > > setup, with the I/O scheduler set to 'none' in both host and guest.
> > > 
> > > The fio workload included sequential and random read/write with varying
> > > numbers of jobs (1,4,8,16) and io_depth of 8. The tests were conducted
> > > with single and dual iothreads, using the newly introduced poll-weight
> > > parameter to measure their impact on CPU cost and throughput.
> > > 
> > > Compared to the baseline, across four FIO workload patterns (sequential
> > > R/W, random R/W), and averaged over FIO job counts of 1, 4, 8, and 16,
> > > throughput decreased slightly (-3% to -8% for one iothread, -2% to -5%
> > > for two iothreads), while CPU usage on the s390x host dropped
> > > significantly (-10% to -25% and -7% to -12%, respectively).
> > Hi Jaehoon,
> > I would like to run the same fio benchmarks on a local NVMe drive (<10us
> > request latency) to see how that type of hardware configuration is
> > affected. Are the scripts and fio job files available somewhere?
> > 
> > Thanks,
> > Stefan
> 
> Thank you for your reply.
> The fio scripts are not available in a location you can access, but there is nothing particularly special in the settings.
> I’m sharing below the methodology and test setup used by our performance team.
> 
> Guest Setup
> ----------------------
> - 12 vCPUs, 4 GiB memory
> - 16 virtio disks based on the FCP multipath devices in the host
> 
> FIO test parameters
> -----------------------
> - FIO Version: fio-3.33
> - Filesize: 2G
> - Blocksize: 8K / 128K
> - Direct I/O: 1
> - FIO I/O Engine: libaio
> - NUMJOB List: 1, 4, 8, 16
> - IODEPTH: 8
> - Runtime (s): 150
> 
> Two FIO samples for random read
> --------------------------------
> fio --direct=1 --name=test --numjobs=16 --filename=base.0.0:base.1.0:base.2.0:base.3.0:base.4.0:base.5.0:base.6.0:base.7.0:base.8.0:base.9.0:base.10.0:base.11.0:base.12.0:base.13.0:base.14.0:base.15.0 --size=32G  --time_based --runtime=4m --readwrite=randread --ioengine=libaio --iodepth=8 --bs=8k
> fio --direct=1 --name=test --numjobs=4  --filename=subw1/base.0.0:subw4/base.3.0:subw8/base.7.0:subw12/base.11.0:subw16/base.15.0                                                                        --size=8G   --time_based --runtime=4m --readwrite=randread --ioengine=libaio --iodepth=8 --bs=8k
> 
> 
> additional notes
> ----------------
> - Each file is placed on a separate disk device mounted under subw<n> as specified in --filename=....
> - We execute one warmup run, then two measurement runs and calculate the average

Thanks, I will share x86_64 with fast local NVMe results when I have collected them.

Stefan

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