block: remove the anticipatory IO scheduler

AS is mostly a subset of CFQ, so there's little point in still
providing this separate IO scheduler. Hopefully at some point we
can get down to one single IO scheduler again, at least this brings
us closer by having only one intelligent IO scheduler.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 4 insertions, 18 deletions

diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index 7e803fc88770..baad3dae3655 100644
--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -12,24 +12,14 @@ config IOSCHED_NOOP
           that do their own scheduling and require only minimal assistance from
           the kernel.
 
-config IOSCHED_AS
-        tristate "Anticipatory I/O scheduler"
-        default y
-        ---help---
-          The anticipatory I/O scheduler is generally a good choice for most
-          environments, but is quite large and complex when compared to the
-          deadline I/O scheduler, it can also be slower in some cases
-          especially some database loads.
-
 config IOSCHED_DEADLINE
         tristate "Deadline I/O scheduler"
         default y
         ---help---
-          The deadline I/O scheduler is simple and compact, and is often as
-          good as the anticipatory I/O scheduler, and in some database
-          workloads, better. In the case of a single process performing I/O to
-          a disk at any one time, its behaviour is almost identical to the
-          anticipatory I/O scheduler and so is a good choice.
+          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"
@@ -47,9 +37,6 @@ choice
           Select the I/O scheduler which will be used by default for all
           block devices.
 
-        config DEFAULT_AS
-                bool "Anticipatory" if IOSCHED_AS=y
-
         config DEFAULT_DEADLINE
                 bool "Deadline" if IOSCHED_DEADLINE=y
 
@@ -63,7 +50,6 @@ endchoice
 
 config DEFAULT_IOSCHED
         string
-        default "anticipatory" if DEFAULT_AS
         default "deadline" if DEFAULT_DEADLINE
         default "cfq" if DEFAULT_CFQ
         default "noop" if DEFAULT_NOOP