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Subject[PATCH V2 10/10] doc, bfq-iosched: make it consistent with the new cgroup interface
Date
BFQ now shares interface files with CFQ, for the proportional-share
policy. Make documentation consistent with that.

Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
---
Documentation/block/bfq-iosched.txt | 28 +++++++++++++++-------------
1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/Documentation/block/bfq-iosched.txt b/Documentation/block/bfq-iosched.txt
index 6d7dd5ab8554..3d7ef138ce6a 100644
--- a/Documentation/block/bfq-iosched.txt
+++ b/Documentation/block/bfq-iosched.txt
@@ -508,12 +508,14 @@ 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 uses the standard interface files of the proportional-share
+policy, previously used by CFQ. If one such file is read/written, then
+the operation associated with the file is performed by BFQ for each
+device where BFQ is the active scheduler. In addition, BFQ is
+configured so as to share interface files with other entities (if some
+of these files does happen to be shared, then its associated operation
+is performed also by any of the other entities that is using the
+file).

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 +523,13 @@ 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
-blkio.bfq.io_service_bytes
-blkio.bfq.io_service_bytes_recursive
-blkio.bfq.io_serviced
-blkio.bfq.io_serviced_recursive
+blkio.io_service_bytes
+blkio.io_service_bytes_recursive
+blkio.io_serviced
+blkio.io_serviced_recursive

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
CONFIG_DEBUG_BLK_CGROUP.

@@ -536,8 +538,8 @@ 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.
--
2.16.1
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