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

[Xose Vazquez Perez <xose.vazquez@gmail.com>]

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