On Sat, Mar 18, 2017 at 6:46 PM, Bart Van Assche
[off-list ref] wrote:

On Sat, 2017-03-18 at 18:09 +0100, Linus Walleij wrote:

quoted

On Sat, Mar 18, 2017 at 11:52 AM, Paolo Valente
[off-list ref] wrote:

quoted

quoted

Il giorno 14 mar 2017, alle ore 16:32, Bart Van Assche [off-list ref] ha scritto:
(...) what should
a developer do who only has access to a small subset of all the storage
devices that are supported by the Linux kernel and hence who can not run the
benchmark against every supported storage device?

Don't we use the community for that? We are dependent on people
downloading and testing our code eventually, I mean sure it's good if
we make some reasonable effort to test changes we do, but we are
only humans, and we get corrected by the experience of other humans.

Hello Linus,

Do you mean relying on the community to test other storage devices before
or after a patch is upstream?

I guess they should test it when it is in linux-next?

Relying on the community to file bug reports
after a patch is upstream would be wrong. The Linux kernel should not be
used for experiments. As you know patches that are sent upstream should
not introduce regressions.

Yeah still people introduce regressions and we have 7-8 release
candidates for each kernel because of this. Humans have flaws
I guess.

My primary concern about BFQ is that it is a very complicated I/O scheduler
and also that the concepts used internally in that I/O scheduler are far
away from the concepts we are used to when reasoning about I/O devices. I'm
concerned that this will make the BFQ I/O scheduler hard to maintain.

I understand that. Let's follow all rules of thumb that make code
easy to maintain.

We have pretty broad agreement on what makes code easy to
maintain on the syntactic level, checkpatch and some manual inspection
easily gives that.

I think where we need the most brainshare is in how to make semantics
maintainable. It's no fun reading terse code and try to figure out how
the developer writing it was thinking, so let's focus on anything we do not
understand and make it understandable, it seems Paolo is onto this task
for what I can tell.

Yours,
Linus Walleij