Re: bfq-mq performance comparison to cfq

Paolo Valente
2017-04-11T07:29:46Z

> Il giorno 10 apr 2017, alle ore 17:15, Bart Van Assche =
<bart.vanassche@sandisk.com> ha scritto:
>=20
> On Mon, 2017-04-10 at 11:55 +0200, Paolo Valente wrote:
>> That said, if you do always want maximum throughput, even at the
>> expense of latency, then just switch off low-latency heuristics, =
i.e.,
>> set low_latency to 0. Depending on the device, setting slice_ilde to
>> 0 may help a lot too (as well as with CFQ). If the throughput is
>> still low also after forcing BFQ to an only-throughput mode, then you
>> hit some bug, and I'll have a little more work to do ...
>=20
> Hello Paolo,
>=20
> Has it been considered to make applications tell the I/O scheduler
> whether to optimize for latency or for throughput? It shouldn't be =
that
> hard for window managers and shells to figure out whether or not a new
> application that is being started is interactive or not. This would
> require a mechanism that allows applications to provide such =
information
> to the I/O scheduler. Wouldn't that be a better approach than the I/O
> scheduler trying to guess whether or not an application is an =
interactive
> application?
>=20

IMO that would be an (or maybe the) optimal solution, in terms of both
throughput and latency. We have even developed a prototype doing what
you propose, for Android. Unfortunately, I have not yet succeeded in
getting support, to turn it into candidate production code, or to make
a similar solution for lsb-compliant systems.

Thanks,
Paolo

> Bart.