Commit df668a5f authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'for-5.14/block-2021-06-29' of git://git.kernel.dk/linux-block 

Pull core block updates from Jens Axboe:

 - disk events cleanup (Christoph)

 - gendisk and request queue allocation simplifications (Christoph)

 - bdev_disk_changed cleanups (Christoph)

 - IO priority improvements (Bart)

 - Chained bio completion trace fix (Edward)

 - blk-wbt fixes (Jan)

 - blk-wbt enable/disable fix (Zhang)

 - Scheduler dispatch improvements (Jan, Ming)

 - Shared tagset scheduler improvements (John)

 - BFQ updates (Paolo, Luca, Pietro)

 - BFQ lock inversion fix (Jan)

 - Documentation improvements (Kir)

 - CLONE_IO block cgroup fix (Tejun)

 - Remove of ancient and deprecated block dump feature (zhangyi)

 - Discard merge fix (Ming)

 - Misc fixes or followup fixes (Colin, Damien, Dan, Long, Max, Thomas,
   Yang)

* tag 'for-5.14/block-2021-06-29' of git://git.kernel.dk/linux-block: (129 commits)
  block: fix discard request merge
  block/mq-deadline: Remove a WARN_ON_ONCE() call
  blk-mq: update hctx->dispatch_busy in case of real scheduler
  blk: Fix lock inversion between ioc lock and bfqd lock
  bfq: Remove merged request already in bfq_requests_merged()
  block: pass a gendisk to bdev_disk_changed
  block: move bdev_disk_changed
  block: add the events* attributes to disk_attrs
  block: move the disk events code to a separate file
  block: fix trace completion for chained bio
  block/partitions/msdos: Fix typo inidicator -> indicator
  block, bfq: reset waker pointer with shared queues
  block, bfq: check waker only for queues with no in-flight I/O
  block, bfq: avoid delayed merge of async queues
  block, bfq: boost throughput by extending queue-merging times
  block, bfq: consider also creation time in delayed stable merge
  block, bfq: fix delayed stable merge check
  block, bfq: let also stably merged queues enjoy weight raising
  blk-wbt: make sure throttle is enabled properly
  blk-wbt: introduce a new disable state to prevent false positive by rwb_enabled()
  ...
parents df04fbe8 2705dfb2

Documentation/admin-guide/cgroup-v1/blkio-controller.rst

+80 −75
Original line number Diff line number Diff line
@@ -17,29 +17,30 @@ level logical devices like device mapper. 


HOWTO

=====



Throttling/Upper Limit policy

-----------------------------

- Enable Block IO controller::

Enable Block IO controller::



	CONFIG_BLK_CGROUP=y



- Enable throttling in block layer::

Enable throttling in block layer::



	CONFIG_BLK_DEV_THROTTLING=y



- Mount blkio controller (see cgroups.txt, Why are cgroups needed?)::

Mount blkio controller (see cgroups.txt, Why are cgroups needed?)::



        mount -t cgroup -o blkio none /sys/fs/cgroup/blkio



- Specify a bandwidth rate on particular device for root group. The format

Specify a bandwidth rate on particular device for root group. The format

for policy is "<major>:<minor>  <bytes_per_second>"::



        echo "8:16  1048576" > /sys/fs/cgroup/blkio/blkio.throttle.read_bps_device



  Above will put a limit of 1MB/second on reads happening for root group

This will put a limit of 1MB/second on reads happening for root group

on device having major/minor number 8:16.



- Run dd to read a file and see if rate is throttled to 1MB/s or not::

Run dd to read a file and see if rate is throttled to 1MB/s or not::



        # dd iflag=direct if=/mnt/common/zerofile of=/dev/null bs=4K count=1024

        1024+0 records in
@@ -79,85 +80,89 @@ following:: 


Various user visible config options

===================================



  CONFIG_BLK_CGROUP

	- Block IO controller.

	  Block IO controller.



  CONFIG_BFQ_CGROUP_DEBUG

	- Debug help. Right now some additional stats file show up in cgroup

	  Debug help. Right now some additional stats file show up in cgroup

	  if this option is enabled.



  CONFIG_BLK_DEV_THROTTLING

	- Enable block device throttling support in block layer.

	  Enable block device throttling support in block layer.



Details of cgroup files

=======================



Proportional weight policy files

--------------------------------

- blkio.weight

	- Specifies per cgroup weight. This is default weight of the group

	  on all the devices until and unless overridden by per device rule.

	  (See blkio.weight_device).

	  Currently allowed range of weights is from 10 to 1000.



- blkio.weight_device

	- One can specify per cgroup per device rules using this interface.

	  These rules override the default value of group weight as specified

	  by blkio.weight.

  blkio.bfq.weight

	  Specifies per cgroup weight. This is default weight of the group

	  on all the devices until and unless overridden by per device rule

	  (see `blkio.bfq.weight_device` below).



	  Currently allowed range of weights is from 1 to 1000. For more details,

          see Documentation/block/bfq-iosched.rst.



  blkio.bfq.weight_device

          Specifes per cgroup per device weights, overriding the default group

          weight. For more details, see Documentation/block/bfq-iosched.rst.



	  Following is the format::



	    # echo dev_maj:dev_minor weight > blkio.weight_device

	    # echo dev_maj:dev_minor weight > blkio.bfq.weight_device



	  Configure weight=300 on /dev/sdb (8:16) in this cgroup::



	    # echo 8:16 300 > blkio.weight_device

	    # cat blkio.weight_device

	    # echo 8:16 300 > blkio.bfq.weight_device

	    # cat blkio.bfq.weight_device

	    dev     weight

	    8:16    300



	  Configure weight=500 on /dev/sda (8:0) in this cgroup::



	    # echo 8:0 500 > blkio.weight_device

	    # cat blkio.weight_device

	    # echo 8:0 500 > blkio.bfq.weight_device

	    # cat blkio.bfq.weight_device

	    dev     weight

	    8:0     500

	    8:16    300



	  Remove specific weight for /dev/sda in this cgroup::



	    # echo 8:0 0 > blkio.weight_device

	    # cat blkio.weight_device

	    # echo 8:0 0 > blkio.bfq.weight_device

	    # cat blkio.bfq.weight_device

	    dev     weight

	    8:16    300



- blkio.time

	- disk time allocated to cgroup per device in milliseconds. First

  blkio.time

	  Disk time allocated to cgroup per device in milliseconds. First

	  two fields specify the major and minor number of the device and

	  third field specifies the disk time allocated to group in

	  milliseconds.



- blkio.sectors

	- number of sectors transferred to/from disk by the group. First

  blkio.sectors

	  Number of sectors transferred to/from disk by the group. First

	  two fields specify the major and minor number of the device and

	  third field specifies the number of sectors transferred by the

	  group to/from the device.



- blkio.io_service_bytes

	- Number of bytes transferred to/from the disk by the group. These

  blkio.io_service_bytes

	  Number of bytes transferred to/from the disk by the group. These

	  are further divided by the type of operation - read or write, sync

	  or async. First two fields specify the major and minor number of the

	  device, third field specifies the operation type and the fourth field

	  specifies the number of bytes.



- blkio.io_serviced

	- Number of IOs (bio) issued to the disk by the group. These

  blkio.io_serviced

	  Number of IOs (bio) issued to the disk by the group. These

	  are further divided by the type of operation - read or write, sync

	  or async. First two fields specify the major and minor number of the

	  device, third field specifies the operation type and the fourth field

	  specifies the number of IOs.



- blkio.io_service_time

	- Total amount of time between request dispatch and request completion

  blkio.io_service_time

	  Total amount of time between request dispatch and request completion

	  for the IOs done by this cgroup. This is in nanoseconds to make it

	  meaningful for flash devices too. For devices with queue depth of 1,

	  this time represents the actual service time. When queue_depth > 1,
@@ -170,8 +175,8 @@ Proportional weight policy files 
	  specifies the operation type and the fourth field specifies the

	  io_service_time in ns.



- blkio.io_wait_time

	- Total amount of time the IOs for this cgroup spent waiting in the

  blkio.io_wait_time

	  Total amount of time the IOs for this cgroup spent waiting in the

	  scheduler queues for service. This can be greater than the total time

	  elapsed since it is cumulative io_wait_time for all IOs. It is not a

	  measure of total time the cgroup spent waiting but rather a measure of
@@ -185,24 +190,24 @@ Proportional weight policy files 
	  minor number of the device, third field specifies the operation type

	  and the fourth field specifies the io_wait_time in ns.



- blkio.io_merged

	- Total number of bios/requests merged into requests belonging to this

  blkio.io_merged

	  Total number of bios/requests merged into requests belonging to this

	  cgroup. This is further divided by the type of operation - read or

	  write, sync or async.



- blkio.io_queued

	- Total number of requests queued up at any given instant for this

  blkio.io_queued

	  Total number of requests queued up at any given instant for this

	  cgroup. This is further divided by the type of operation - read or

	  write, sync or async.



- blkio.avg_queue_size

	- Debugging aid only enabled if CONFIG_BFQ_CGROUP_DEBUG=y.

  blkio.avg_queue_size

	  Debugging aid only enabled if CONFIG_BFQ_CGROUP_DEBUG=y.

	  The average queue size for this cgroup over the entire time of this

	  cgroup's existence. Queue size samples are taken each time one of the

	  queues of this cgroup gets a timeslice.



- blkio.group_wait_time

	- Debugging aid only enabled if CONFIG_BFQ_CGROUP_DEBUG=y.

  blkio.group_wait_time

	  Debugging aid only enabled if CONFIG_BFQ_CGROUP_DEBUG=y.

	  This is the amount of time the cgroup had to wait since it became busy

	  (i.e., went from 0 to 1 request queued) to get a timeslice for one of

	  its queues. This is different from the io_wait_time which is the
@@ -212,8 +217,8 @@ Proportional weight policy files 
	  will only report the group_wait_time accumulated till the last time it

	  got a timeslice and will not include the current delta.



- blkio.empty_time

	- Debugging aid only enabled if CONFIG_BFQ_CGROUP_DEBUG=y.

  blkio.empty_time

	  Debugging aid only enabled if CONFIG_BFQ_CGROUP_DEBUG=y.

	  This is the amount of time a cgroup spends without any pending

	  requests when not being served, i.e., it does not include any time

	  spent idling for one of the queues of the cgroup. This is in
@@ -221,8 +226,8 @@ Proportional weight policy files 
	  the stat will only report the empty_time accumulated till the last

	  time it had a pending request and will not include the current delta.



- blkio.idle_time

	- Debugging aid only enabled if CONFIG_BFQ_CGROUP_DEBUG=y.

  blkio.idle_time

	  Debugging aid only enabled if CONFIG_BFQ_CGROUP_DEBUG=y.

	  This is the amount of time spent by the IO scheduler idling for a

	  given cgroup in anticipation of a better request than the existing ones

	  from other queues/cgroups. This is in nanoseconds. If this is read
@@ -230,43 +235,43 @@ Proportional weight policy files 
	  idle_time accumulated till the last idle period and will not include

	  the current delta.



- blkio.dequeue

	- Debugging aid only enabled if CONFIG_BFQ_CGROUP_DEBUG=y. This

  blkio.dequeue

	  Debugging aid only enabled if CONFIG_BFQ_CGROUP_DEBUG=y. This

	  gives the statistics about how many a times a group was dequeued

	  from service tree of the device. First two fields specify the major

	  and minor number of the device and third field specifies the number

	  of times a group was dequeued from a particular device.



- blkio.*_recursive

	- Recursive version of various stats. These files show the

  blkio.*_recursive

	  Recursive version of various stats. These files show the

          same information as their non-recursive counterparts but

          include stats from all the descendant cgroups.



Throttling/Upper limit policy files

-----------------------------------

- blkio.throttle.read_bps_device

	- Specifies upper limit on READ rate from the device. IO rate is

  blkio.throttle.read_bps_device

	  Specifies upper limit on READ rate from the device. IO rate is

	  specified in bytes per second. Rules are per device. Following is

	  the format::



	    echo "<major>:<minor>  <rate_bytes_per_second>" > /cgrp/blkio.throttle.read_bps_device



- blkio.throttle.write_bps_device

	- Specifies upper limit on WRITE rate to the device. IO rate is

  blkio.throttle.write_bps_device

	  Specifies upper limit on WRITE rate to the device. IO rate is

	  specified in bytes per second. Rules are per device. Following is

	  the format::



	    echo "<major>:<minor>  <rate_bytes_per_second>" > /cgrp/blkio.throttle.write_bps_device



- blkio.throttle.read_iops_device

	- Specifies upper limit on READ rate from the device. IO rate is

  blkio.throttle.read_iops_device

	  Specifies upper limit on READ rate from the device. IO rate is

	  specified in IO per second. Rules are per device. Following is

	  the format::



	   echo "<major>:<minor>  <rate_io_per_second>" > /cgrp/blkio.throttle.read_iops_device



- blkio.throttle.write_iops_device

	- Specifies upper limit on WRITE rate to the device. IO rate is

  blkio.throttle.write_iops_device

	  Specifies upper limit on WRITE rate to the device. IO rate is

	  specified in io per second. Rules are per device. Following is

	  the format::
@@ -275,15 +280,15 @@ Throttling/Upper limit policy files 
          Note: If both BW and IOPS rules are specified for a device, then IO is

          subjected to both the constraints.



- blkio.throttle.io_serviced

	- Number of IOs (bio) issued to the disk by the group. These

  blkio.throttle.io_serviced

	  Number of IOs (bio) issued to the disk by the group. These

	  are further divided by the type of operation - read or write, sync

	  or async. First two fields specify the major and minor number of the

	  device, third field specifies the operation type and the fourth field

	  specifies the number of IOs.



- blkio.throttle.io_service_bytes

	- Number of bytes transferred to/from the disk by the group. These

  blkio.throttle.io_service_bytes

	  Number of bytes transferred to/from the disk by the group. These

	  are further divided by the type of operation - read or write, sync

	  or async. First two fields specify the major and minor number of the

	  device, third field specifies the operation type and the fourth field
@@ -291,6 +296,6 @@ Note: If both BW and IOPS rules are specified for a device, then IO is 


Common files among various policies

-----------------------------------

- blkio.reset_stats

	- Writing an int to this file will result in resetting all the stats

  blkio.reset_stats

	  Writing an int to this file will result in resetting all the stats

	  for that cgroup.

Documentation/admin-guide/cgroup-v2.rst

+55 −0
Original line number Diff line number Diff line
@@ -56,6 +56,7 @@ 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
@@ -1866,6 +1867,60 @@ 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

---

Documentation/admin-guide/laptops/laptop-mode.rst

+0 −11
Original line number Diff line number Diff line
@@ -101,17 +101,6 @@ this results in concentration of disk activity in a small time interval which 
occurs only once every 10 minutes, or whenever the disk is forced to spin up by

a cache miss. The disk can then be spun down in the periods of inactivity.



If you want to find out which process caused the disk to spin up, you can

gather information by setting the flag /proc/sys/vm/block_dump. When this flag

is set, Linux reports all disk read and write operations that take place, and

all block dirtyings done to files. This makes it possible to debug why a disk

needs to spin up, and to increase battery life even more. The output of

block_dump is written to the kernel output, and it can be retrieved using

"dmesg". When you use block_dump and your kernel logging level also includes

kernel debugging messages, you probably want to turn off klogd, otherwise

the output of block_dump will be logged, causing disk activity that is not

normally there.





Configuration

-------------

Documentation/admin-guide/sysctl/vm.rst

+0 −8
Original line number Diff line number Diff line
@@ -25,7 +25,6 @@ files can be found in mm/swap.c. 
Currently, these files are in /proc/sys/vm:



- admin_reserve_kbytes

- block_dump

- compact_memory

- compaction_proactiveness

- compact_unevictable_allowed
@@ -106,13 +105,6 @@ On x86_64 this is about 128MB. 
Changing this takes effect whenever an application requests memory.





block_dump

==========



block_dump enables block I/O debugging when set to a nonzero value. More

information on block I/O debugging is in Documentation/admin-guide/laptops/laptop-mode.rst.





compact_memory

==============

Documentation/block/bfq-iosched.rst

+27 −11
Original line number Diff line number Diff line
@@ -553,14 +553,21 @@ throughput sustainable with bfq, because updating the blkio.bfq.* 
stats is rather costly, especially for some of the stats enabled by

CONFIG_BFQ_CGROUP_DEBUG.



Parameters to set

-----------------

Parameters

----------



For each group, the following parameters can be set:



  weight

        This specifies the default weight for the cgroup inside its parent.

        Available values: 1..1000 (default: 100).



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

        For cgroup v1, it is set by writing the value to `blkio.bfq.weight`.



weight (namely blkio.bfq.weight or io.bfq-weight): the weight of the

group inside its parent. Available values: 1..1000 (default 100). The

linear mapping between ioprio and weights, described at the beginning

        For cgroup v2, it is set by writing the value to `io.bfq.weight`.

        (with an optional prefix of `default` and a space).



        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.
@@ -568,6 +575,15 @@ Recall that, if low-latency is set, then BFQ automatically raises the 
        weight of the queues associated with interactive and soft real-time

        applications. Unset this tunable if you need/want to control weights.



  weight_device

        This specifies a per-device weight for the cgroup. The syntax is

        `minor:major weight`. A weight of `0` may be used to reset to the default

        weight.



        For cgroup v1, it is set by writing the value to `blkio.bfq.weight_device`.



        For cgroup v2, the file name is `io.bfq.weight`.





[1]

    P. Valente, A. Avanzini, "Evolution of the BFQ Storage I/O