[Angstrom-devel] [RFC] Using IOSCHED_NOOP as the default for linux-handhelds

[pHilipp Zabel]

On Feb 10, 2008 10:07 PM, Paul Sokolovsky <pmiscml at gmail.com> wrote:
> Hello,
>
> Looking for what more stuff can be made modular, I'd like to make
> IOSCHED_NOOP the default, builtin scheduler and make all other IO
> schedulers modules. Current default is the anticipatory one. From
> linux/block/Kconfig.iosched:
>
> config IOSCHED_NOOP
>         bool
>         default y
>         ---help---
>           The no-op I/O scheduler is a minimal scheduler that does
> basic merging
>           and sorting. Its main uses include non-disk based block
> devices like
>           memory devices, and specialised software or hardware
> environments
>           that do their own scheduling and require only minimal
> assistance from
>           the kernel.
>
> config IOSCHED_AS
>         tristate "Anticipatory I/O scheduler"
>         default y
>         ---help---
>           The anticipatory I/O scheduler is generally a good choice for
> most
>           environments, but is quite large and complex when compared to
> the
>           deadline I/O scheduler, it can also be slower in some cases
>           especially some database loads.
>
>
> IMHO, noop's description is good enough for builtin flash and flash
> cards. I have no idea why IOSCHED_AS is used (pristine default is
> IOSCHED_CFQ), but it is the same as used by linux-rp, so I assume
> that's where it come from. So, I cc: Richard Purdie to ask if there're
> good grounds for that and to draw attention that it's a chance to
> recover some 5K for kernelspace-starving Z devices.

That sounds sane enough to me.
Has anybody ever done benchmarks with the different schedulers on
MTD/MMC/CF flash storage? Without knowing much about how AS or CFQ
work, I'd even expect the noop scheduler to be the fastest here.
Although, isn't there one zaurus that can boot directly from the
internal microdrive?

regards
Philipp