Currently, CFQ IO scheduler uses it to recognize task groups and
control disk bandwidth allocation (proportional time slice allocation)
- to such task groups.
+ to such task groups. It is also used by bio throttling logic in
+ block layer to implement upper limit in IO rates on a device.
This option only enables generic Block IO controller infrastructure.
- One needs to also enable actual IO controlling logic in CFQ for it
- to take effect. (CONFIG_CFQ_GROUP_IOSCHED=y).
+ One needs to also enable actual IO controlling logic/policy. For
+ enabling proportional weight division of disk bandwidth in CFQ seti
+ CONFIG_CFQ_GROUP_IOSCHED=y and for enabling throttling policy set
+ CONFIG_BLK_THROTTLE=y.
See Documentation/cgroups/blkio-controller.txt for more information.
bool
config SYSFS_DEPRECATED
- bool
-
-config SYSFS_DEPRECATED_V2
bool "enable deprecated sysfs features to support old userspace tools"
depends on SYSFS
default n
- select SYSFS_DEPRECATED
- help
- This option switches the layout of sysfs to the deprecated
- version. Do not use it on recent distributions.
-
- The current sysfs layout features a unified device tree at
- /sys/devices/, which is able to express a hierarchy between
- class devices. If the deprecated option is set to Y, the
- unified device tree is split into a bus device tree at
- /sys/devices/ and several individual class device trees at
- /sys/class/. The class and bus devices will be connected by
- "<subsystem>:<name>" and the "device" links. The "block"
- class devices, will not show up in /sys/class/block/. Some
- subsystems will suppress the creation of some devices which
- depend on the unified device tree.
-
- This option is not a pure compatibility option that can
- be safely enabled on newer distributions. It will change the
- layout of sysfs to the non-extensible deprecated version,
- and disable some features, which can not be exported without
- confusing older userspace tools. Since 2007/2008 all major
- distributions do not enable this option, and ship no tools which
- depend on the deprecated layout or this option.
-
- If you are using a new kernel on an older distribution, or use
- older userspace tools, you might need to say Y here. Do not say Y,
- if the original kernel, that came with your distribution, has
- this option set to N.
+ help
+ This option adds code that switches the layout of the "block" class
+ devices, to not show up in /sys/class/block/, but only in
+ /sys/block/.
+
+ This switch is only active when the sysfs.deprecated=1 boot option is
+ passed or the SYSFS_DEPRECATED_V2 option is set.
+
+ This option allows new kernels to run on old distributions and tools,
+ which might get confused by /sys/class/block/. Since 2007/2008 all
+ major distributions and tools handle this just fine.
+
+ Recent distributions and userspace tools after 2009/2010 depend on
+ the existence of /sys/class/block/, and will not work with this
+ option enabled.
+
+ Only if you are using a new kernel on an old distribution, you might
+ need to say Y here.
+
+config SYSFS_DEPRECATED_V2
+ bool "enabled deprecated sysfs features by default"
+ default n
+ depends on SYSFS
+ depends on SYSFS_DEPRECATED
+ help
+ Enable deprecated sysfs by default.
+
+ See the CONFIG_SYSFS_DEPRECATED option for more details about this
+ option.
+
+ Only if you are using a new kernel on an old distribution, you might
+ need to say Y here. Even then, odds are you would not need it
+ enabled, you can always pass the boot option if absolutely necessary.
config RELAY
bool "Kernel->user space relay support (formerly relayfs)"
git.openpandora.org / pandora-kernel.git / blobdiff