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Subject[PATCH 12/12] doc, bfq-iosched: make it consistent with the new cgroup interface
BFQ now shares interface files with CFQ, for the proportional-share
policy. Make documentation consistent with that.

Signed-off-by: Paolo Valente <>
Documentation/block/bfq-iosched.txt | 25 ++++++++++++-------------
1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/Documentation/block/bfq-iosched.txt b/Documentation/block/bfq-iosched.txt
index 6d7dd5ab8554..b1faf091266e 100644
--- a/Documentation/block/bfq-iosched.txt
+++ b/Documentation/block/bfq-iosched.txt
@@ -508,12 +508,11 @@ process.
To get proportional sharing of bandwidth with BFQ for a given device,
BFQ must of course be the active scheduler for that device.

-Within each group directory, the names of the files associated with
-BFQ-specific cgroup parameters and stats begin with the "bfq."
-prefix. So, with cgroups-v1 or cgroups-v2, the full prefix for
-BFQ-specific files is "blkio.bfq." or "io.bfq." For example, the group
-parameter to set the weight of a group with BFQ is blkio.bfq.weight
-or io.bfq.weight.
+BFQ shares interface files with CFQ. So, if one reads/writes a file
+provided by the proportional share policy for a group, then the
+associated operation is performed by/on BFQ for each device where BFQ
+is the active scheduler, and by/on CFQ for each device where CFQ is
+the active scheduler.

As for cgroups-v1 (blkio controller), the exact set of stat files
created, and kept up-to-date by bfq, depends on whether
@@ -521,13 +520,13 @@ CONFIG_DEBUG_BLK_CGROUP is set. If it is set, then bfq creates all
the stat files documented in
Documentation/cgroup-v1/blkio-controller.txt. If, instead,
CONFIG_DEBUG_BLK_CGROUP is not set, then bfq creates only the files

The value of CONFIG_DEBUG_BLK_CGROUP greatly influences the maximum
-throughput sustainable with bfq, because updating the blkio.bfq.*
+throughput sustainable with BFQ, because updating the blkio.*
stats is rather costly, especially for some of the stats enabled by

@@ -536,8 +535,8 @@ Parameters to set

For each group, there is only the following parameter to set.

-weight (namely blkio.bfq.weight or io.bfq-weight): the weight of the
-group inside its parent. Available values: 1..10000 (default 100). The
+weight (namely blkio.weight or io.weight): the weight of the group
+inside its parent. Available values: 1..10000 (default 100). The
linear mapping between ioprio and weights, described at the beginning
of the tunable section, is still valid, but all weights higher than
IOPRIO_BE_NR*10 are mapped to ioprio 0.
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