Re: [RFC PATCH] block: Change default IO scheduler to deadline exceptSATA

[Xose Vazquez Perez]

Vivek Goyal wrote:

> I am wondering if CFQ as default scheduler is still the right choice. CFQ
> generally works well on slow rotational media (SATA?). But often
> underperforms on faster storage (storage arrays, PCIE SSDs, virtualized
> disk in linux guests etc). People often put logic in user space to tune their
> systems and change IO scheduler to deadline to get better performance on
> faster storage.
>
> Though there is not one good answer for all kind of storage and for all
> kind of workloads, I am wondering if we can provide a better default and
> that is change default IO scheduler to "deadline" except SATA.
>
> One can argue that some SAS disks can be slow too and benefit from CFQ. Yes,
> but default IO scheduler choice is not perfect anyway. It just tries to
> cater to a wide variety of use cases out of the box.
>
> So I am throwing this patch out see if it flies. Personally, I think it
> might turn out to be a more reasonable default.

done time ago for dasd devices.

chuchi:~/curre/linux-2.6 $ grep -ri deadline drivers/s390/block/*
drivers/s390/block/dasd.c:      rc = elevator_init(block->request_queue, "deadline");
drivers/s390/block/Kconfig:     select IOSCHED_DEADLINE
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