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FROMGIT: block: Introduce the ioprio rq-qos policy

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Introduce an rq-qos policy that assigns an I/O priority to requests based
on blk-cgroup configuration settings. This policy has the following
advantages over the ioprio_set() system call:
- This policy is cgroup based so it has all the advantages of cgroups.
- While ioprio_set() does not affect page cache writeback I/O, this rq-qos
  controller affects page cache writeback I/O for filesystems that support
  assiociating a cgroup with writeback I/O. See also
  Documentation/admin-guide/cgroup-v2.rst.

Cc: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
BUG: 187357408
Change-Id: If51e608ad37ee7a3f57b507bb17900dcfcb263ed
(cherry picked from commit ee9d2a55c960f152b5710078bbe399a4c51eb0a9 git://git.kernel.dk/linux-block/ for-5.14/block)
Signed-off-by: Bart Van Assche <bvanassche@google.com>
This commit is contained in:
Bart Van Assche
2021-06-03 14:49:29 -07:00
committed by Todd Kjos
parent 16b9fe8a3a
commit 46d6ae07a7
8 changed files with 354 additions and 0 deletions
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55
Documentation/admin-guide/cgroup-v2.rst
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@@ -54,6 +54,7 @@ v1 is available under :ref:`Documentation/admin-guide/cgroup-v1/index.rst <cgrou
5-3-3. IO Latency
5-3-3-1. How IO Latency Throttling Works
5-3-3-2. IO Latency Interface Files
5-3-4. IO Priority
5-4. PID
5-4-1. PID Interface Files
5-5. Cpuset
@@ -1848,6 +1849,60 @@ IO Latency Interface Files
duration of time between evaluation events. Windows only elapse
with IO activity. Idle periods extend the most recent window.
IO Priority
~~~~~~~~~~~
A single attribute controls the behavior of the I/O priority cgroup policy,
namely the blkio.prio.class attribute. The following values are accepted for
that attribute:
no-change
Do not modify the I/O priority class.
none-to-rt
For requests that do not have an I/O priority class (NONE),
change the I/O priority class into RT. Do not modify
the I/O priority class of other requests.
restrict-to-be
For requests that do not have an I/O priority class or that have I/O
priority class RT, change it into BE. Do not modify the I/O priority
class of requests that have priority class IDLE.
idle
Change the I/O priority class of all requests into IDLE, the lowest
I/O priority class.
The following numerical values are associated with the I/O priority policies:
+-------------+---+
| no-change | 0 |
+-------------+---+
| none-to-rt | 1 |
+-------------+---+
| rt-to-be | 2 |
+-------------+---+
| all-to-idle | 3 |
+-------------+---+
The numerical value that corresponds to each I/O priority class is as follows:
+-------------------------------+---+
| IOPRIO_CLASS_NONE | 0 |
+-------------------------------+---+
| IOPRIO_CLASS_RT (real-time) | 1 |
+-------------------------------+---+
| IOPRIO_CLASS_BE (best effort) | 2 |
+-------------------------------+---+
| IOPRIO_CLASS_IDLE | 3 |
+-------------------------------+---+
The algorithm to set the I/O priority class for a request is as follows:
- Translate the I/O priority class policy into a number.
- Change the request I/O priority class into the maximum of the I/O priority
class policy number and the numerical I/O priority class.
PID
---