From 18bc095e952d31d5e07b88b8b89fb2ae8c3048ad Mon Sep 17 00:00:00 2001 From: Arianna Avanzini <avanzini.arianna@gmail.com> Date: Sat, 4 Feb 2012 10:55:51 +0100 Subject: [PATCH 1/2] block: cgroups, kconfig, build bits for BFQ-v5r1-3.4

Update Kconfig.iosched to include kernel configuration options
for BFQ. Add a Kconfig option and do the related Makefile changes
to compile the scheduler. Also let the cgroups subsystem know about
the BFQ I/O controller.

Signed-off-by: Paolo Valente <paolo.valente@unimore.it>
Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com>
block: fiops ioscheduler core

FIOPS (Fair IOPS) ioscheduler is IOPS based ioscheduler, so only targets
for drive without I/O seek. It's quite similar like CFQ, but the dispatch
decision is made according to IOPS instead of slice.

The algorithm is simple. Drive has a service tree, and each task lives in
the tree. The key into the tree is called vios (virtual I/O). Every request
has vios, which is calculated according to its ioprio, request size and so
on. Task's vios is the sum of vios of all requests it dispatches. FIOPS
always selects task with minimum vios in the service tree and let the task
dispatch request. The dispatched request's vios is then added to the task's
vios and the task is repositioned in the sevice tree.

Unlike CFQ, FIOPS doesn't have separate sync/async queues, because with I/O
less writeback, usually a task can only dispatch either sync or async requests.
Bias read or write request can still be done with read/write scale.

One issue is if workload iodepth is lower than drive queue_depth, IOPS
share of a task might not be strictly according to its priority, request
size and so on. In this case, the drive is in idle actually. Solving the
problem need make drive idle, so impact performance. I believe CFQ isn't
completely fair between tasks in such case too.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Add SIO I/O scheduler