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if BLOCK
menu "IO Schedulers"
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_DEADLINE
tristate "Deadline I/O scheduler"
default y
---help---
The deadline I/O scheduler is simple and compact. It will provide
CSCAN service with FIFO expiration of requests, switching to
a new point in the service tree and doing a batch of IO from there
in case of expiry.
config IOSCHED_CFQ
tristate "CFQ I/O scheduler"
# If BLK_CGROUP is a module, CFQ has to be built as module.
depends on (BLK_CGROUP=m && m) || !BLK_CGROUP || BLK_CGROUP=y
default y
---help---
The CFQ I/O scheduler tries to distribute bandwidth equally
among all processes in the system. It should provide a fair
and low latency working environment, suitable for both desktop
and server systems.
This is the default I/O scheduler.
Note: If BLK_CGROUP=m, then CFQ can be built only as module.
config CFQ_GROUP_IOSCHED
bool "CFQ Group Scheduling support"
depends on IOSCHED_CFQ && BLK_CGROUP
default n
---help---
Enable group IO scheduling in CFQ.
config IOSCHED_SIO
tristate "Simple I/O scheduler"
default y
---help---
The Simple I/O scheduler is an extremely simple scheduler,
based on noop and deadline, that relies on deadlines to
ensure fairness. The algorithm does not do any sorting but
basic merging, trying to keep a minimum overhead. It is aimed
mainly for aleatory access devices (eg: flash devices).
config IOSCHED_BFQ
tristate "BFQ I/O scheduler"
depends on EXPERIMENTAL
default n
---help---
The BFQ I/O scheduler tries to distribute bandwidth among
all processes according to their weights.
It aims at distributing the bandwidth as desired, independently of
the disk parameters and with any workload. It also tries to
guarantee low latency to interactive and soft real-time
applications. If compiled built-in (saying Y here), BFQ can
be configured to support hierarchical scheduling.
config CGROUP_BFQIO
bool "BFQ hierarchical scheduling support"
depends on CGROUPS && IOSCHED_BFQ=y
default n
---help---
Enable hierarchical scheduling in BFQ, using the cgroups
filesystem interface. The name of the subsystem will be
bfqio.
choice
prompt "Default I/O scheduler"
default DEFAULT_CFQ
help
Select the I/O scheduler which will be used by default for all
block devices.
config DEFAULT_DEADLINE
bool "Deadline" if IOSCHED_DEADLINE=y
config DEFAULT_CFQ
bool "CFQ" if IOSCHED_CFQ=y
config DEFAULT_SIO
bool "SIO" if IOSCHED_SIO=y
config DEFAULT_BFQ
bool "BFQ" if IOSCHED_BFQ=y
config DEFAULT_NOOP
bool "No-op"
endchoice
config DEFAULT_IOSCHED
string
default "deadline" if DEFAULT_DEADLINE
default "cfq" if DEFAULT_CFQ
default "sio" if DEFAULT_SIO
default "bfq" if DEFAULT_BFQ
default "noop" if DEFAULT_NOOP
endmenu
endif
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