Comment # 25 on bug 1134353 from Paolo Valente

(In reply to Andreas Herrmann from comment #24)
> Created attachment 809495 [details]
> comparison generated for io-fio-randread-[a]sync-{seq,rand}write mmtests
> results
> 
> Those looked odd and I double checked that they were reproducible.
> I didn't find flaws in the test setup thus I now report them.
> Maybe there is still some issue with the test -- results for (4)
> look quite odd -- so better try to reproduce yourself.
> Tests were done with kernel 5.2.0-rc3 using ext4 and
> "mitigations=off".
> 
> To summarize:
> (1) io-fio-randread-async-randwrite-ext4-nosecure
>     Seems somehow ok. Higher write throughput allowed by lower read
>     throughput (bfq vs. mq-deadline).
> (2) io-fio-randread-sync-heavywrite-ext4-nosecure
>     Dito but kyber further reduces write throughput with much more
>     gain for reads.
> (3) io-fio-randread-async-seqwrite-ext4-nosecure
>     writes -(7..8%) reads +>2000% for other sched options in
>     comparison to BFQ
> (4) io-fio-randread-sync-randwrite-ext4-nosecure
>     Results are "off the charts". Both latencies (read and write) for
>     BFQ are much worse than all other sched options resulting in much
>     lower throughput for both reads and writes.
> 
> Based on that only mq-deadline and none deliver kind of not-surprising
> performance. The low read throughput of mere 48.64 KiB for
> io-fio-randread-async-seqwrite-ext4-nosecure with BFQ looks
> disturbing.

Thank you very much for these new tests. In the next weeks, I'll look for the
cause of these anomalies, then I'll get back to your dbench results.