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authorSang-Heon Jeon <ekffu200098@gmail.com>2026-08-24 01:18:14 +0900
committerJulia Lawall <Julia.Lawall@inria.fr>2026-08-23 22:12:11 +0200
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treedcc4da1d99f17541c5590ac63c77da4bf372a4ab /Documentation/block/switching-sched.rst
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coccinelle: alloc_cast: drop removed allocatorsgrafted
- pci_alloc_consistent() and pci_zalloc_consistent() were removed by commit 7968778914e5 ("PCI: Remove the deprecated "pci-dma-compat.h" API") - kmem_alloc() was removed by commit f078d4ea8276 ("xfs: convert kmem_alloc() to kmalloc()") - kmem_zalloc() was removed by commit 10634530f7ba ("xfs: convert kmem_zalloc() to kzalloc()") - kmem_zone_alloc() and kmem_zone_zalloc() were removed by commit bae633a4a283 ("xfs: remove xfs_zone_{alloc,zalloc} helpers") So drop them from the rules. No functional change. Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com> Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
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+===================
+Switching Scheduler
+===================
+
+Each io queue has a set of io scheduler tunables associated with it. These
+tunables control how the io scheduler works. You can find these entries
+in::
+
+ /sys/block/<device>/queue/iosched
+
+assuming that you have sysfs mounted on /sys. If you don't have sysfs mounted,
+you can do so by typing::
+
+ # mount none /sys -t sysfs
+
+It is possible to change the IO scheduler for a given block device on
+the fly to select one of mq-deadline, none, bfq, or kyber schedulers -
+which can improve that device's throughput.
+
+To set a specific scheduler, simply do this::
+
+ echo SCHEDNAME > /sys/block/DEV/queue/scheduler
+
+where SCHEDNAME is the name of a defined IO scheduler, and DEV is the
+device name (hda, hdb, sga, or whatever you happen to have).
+
+The list of defined schedulers can be found by simply doing
+a "cat /sys/block/DEV/queue/scheduler" - the list of valid names
+will be displayed, with the currently selected scheduler in brackets::
+
+ # cat /sys/block/sda/queue/scheduler
+ [mq-deadline] kyber bfq none
+ # echo none >/sys/block/sda/queue/scheduler
+ # cat /sys/block/sda/queue/scheduler
+ [none] mq-deadline kyber bfq