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authorLinus Torvalds <torvalds@linux-foundation.org>2018-08-14 10:23:25 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-08-14 10:23:25 -0700
commit73ba2fb33c492916853dfe63e3b3163da0be661d (patch)
treec2fda8ca1273744d2e884d24189a15ac1a7d63c2 /Documentation
parent958f338e96f874a0d29442396d6adf9c1e17aa2d (diff)
parentb86d865cb1cae1e61527ea0b8977078bbf694328 (diff)
downloadlinux-73ba2fb33c492916853dfe63e3b3163da0be661d.tar.bz2
Merge tag 'for-4.19/block-20180812' of git://git.kernel.dk/linux-block
Pull block updates from Jens Axboe: "First pull request for this merge window, there will also be a followup request with some stragglers. This pull request contains: - Fix for a thundering heard issue in the wbt block code (Anchal Agarwal) - A few NVMe pull requests: * Improved tracepoints (Keith) * Larger inline data support for RDMA (Steve Wise) * RDMA setup/teardown fixes (Sagi) * Effects log suppor for NVMe target (Chaitanya Kulkarni) * Buffered IO suppor for NVMe target (Chaitanya Kulkarni) * TP4004 (ANA) support (Christoph) * Various NVMe fixes - Block io-latency controller support. Much needed support for properly containing block devices. (Josef) - Series improving how we handle sense information on the stack (Kees) - Lightnvm fixes and updates/improvements (Mathias/Javier et al) - Zoned device support for null_blk (Matias) - AIX partition fixes (Mauricio Faria de Oliveira) - DIF checksum code made generic (Max Gurtovoy) - Add support for discard in iostats (Michael Callahan / Tejun) - Set of updates for BFQ (Paolo) - Removal of async write support for bsg (Christoph) - Bio page dirtying and clone fixups (Christoph) - Set of bcache fix/changes (via Coly) - Series improving blk-mq queue setup/teardown speed (Ming) - Series improving merging performance on blk-mq (Ming) - Lots of other fixes and cleanups from a slew of folks" * tag 'for-4.19/block-20180812' of git://git.kernel.dk/linux-block: (190 commits) blkcg: Make blkg_root_lookup() work for queues in bypass mode bcache: fix error setting writeback_rate through sysfs interface null_blk: add lock drop/acquire annotation Blk-throttle: reduce tail io latency when iops limit is enforced block: paride: pd: mark expected switch fall-throughs block: Ensure that a request queue is dissociated from the cgroup controller block: Introduce blk_exit_queue() blkcg: Introduce blkg_root_lookup() block: Remove two superfluous #include directives blk-mq: count the hctx as active before allocating tag block: bvec_nr_vecs() returns value for wrong slab bcache: trivial - remove tailing backslash in macro BTREE_FLAG bcache: make the pr_err statement used for ENOENT only in sysfs_attatch section bcache: set max writeback rate when I/O request is idle bcache: add code comments for bset.c bcache: fix mistaken comments in request.c bcache: fix mistaken code comments in bcache.h bcache: add a comment in super.c bcache: avoid unncessary cache prefetch bch_btree_node_get() bcache: display rate debug parameters to 0 when writeback is not running ...
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/ABI/testing/procfs-diskstats10
-rw-r--r--Documentation/admin-guide/cgroup-v2.rst92
-rw-r--r--Documentation/block/null_blk.txt7
-rw-r--r--Documentation/block/stat.txt28
-rw-r--r--Documentation/iostats.txt15
5 files changed, 136 insertions, 16 deletions
diff --git a/Documentation/ABI/testing/procfs-diskstats b/Documentation/ABI/testing/procfs-diskstats
index f91a973a37fe..abac31d216de 100644
--- a/Documentation/ABI/testing/procfs-diskstats
+++ b/Documentation/ABI/testing/procfs-diskstats
@@ -5,6 +5,7 @@ Description:
The /proc/diskstats file displays the I/O statistics
of block devices. Each line contains the following 14
fields:
+
1 - major number
2 - minor mumber
3 - device name
@@ -19,4 +20,13 @@ Description:
12 - I/Os currently in progress
13 - time spent doing I/Os (ms)
14 - weighted time spent doing I/Os (ms)
+
+ Kernel 4.18+ appends four more fields for discard
+ tracking putting the total at 18:
+
+ 15 - discards completed successfully
+ 16 - discards merged
+ 17 - sectors discarded
+ 18 - time spent discarding
+
For more details refer to Documentation/iostats.txt
diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 8a2c52d5c53b..1746131bc9cb 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -51,6 +51,9 @@ v1 is available under Documentation/cgroup-v1/.
5-3. IO
5-3-1. IO Interface Files
5-3-2. Writeback
+ 5-3-3. IO Latency
+ 5-3-3-1. How IO Latency Throttling Works
+ 5-3-3-2. IO Latency Interface Files
5-4. PID
5-4-1. PID Interface Files
5-5. Device
@@ -1314,17 +1317,19 @@ IO Interface Files
Lines are keyed by $MAJ:$MIN device numbers and not ordered.
The following nested keys are defined.
- ====== ===================
+ ====== =====================
rbytes Bytes read
wbytes Bytes written
rios Number of read IOs
wios Number of write IOs
- ====== ===================
+ dbytes Bytes discarded
+ dios Number of discard IOs
+ ====== =====================
An example read output follows:
- 8:16 rbytes=1459200 wbytes=314773504 rios=192 wios=353
- 8:0 rbytes=90430464 wbytes=299008000 rios=8950 wios=1252
+ 8:16 rbytes=1459200 wbytes=314773504 rios=192 wios=353 dbytes=0 dios=0
+ 8:0 rbytes=90430464 wbytes=299008000 rios=8950 wios=1252 dbytes=50331648 dios=3021
io.weight
A read-write flat-keyed file which exists on non-root cgroups.
@@ -1446,6 +1451,85 @@ writeback as follows.
vm.dirty[_background]_ratio.
+IO Latency
+~~~~~~~~~~
+
+This is a cgroup v2 controller for IO workload protection. You provide a group
+with a latency target, and if the average latency exceeds that target the
+controller will throttle any peers that have a lower latency target than the
+protected workload.
+
+The limits are only applied at the peer level in the hierarchy. This means that
+in the diagram below, only groups A, B, and C will influence each other, and
+groups D and F will influence each other. Group G will influence nobody.
+
+ [root]
+ / | \
+ A B C
+ / \ |
+ D F G
+
+
+So the ideal way to configure this is to set io.latency in groups A, B, and C.
+Generally you do not want to set a value lower than the latency your device
+supports. Experiment to find the value that works best for your workload.
+Start at higher than the expected latency for your device and watch the
+avg_lat value in io.stat for your workload group to get an idea of the
+latency you see during normal operation. Use the avg_lat value as a basis for
+your real setting, setting at 10-15% higher than the value in io.stat.
+
+How IO Latency Throttling Works
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+io.latency is work conserving; so as long as everybody is meeting their latency
+target the controller doesn't do anything. Once a group starts missing its
+target it begins throttling any peer group that has a higher target than itself.
+This throttling takes 2 forms:
+
+- Queue depth throttling. This is the number of outstanding IO's a group is
+ allowed to have. We will clamp down relatively quickly, starting at no limit
+ and going all the way down to 1 IO at a time.
+
+- Artificial delay induction. There are certain types of IO that cannot be
+ throttled without possibly adversely affecting higher priority groups. This
+ includes swapping and metadata IO. These types of IO are allowed to occur
+ normally, however they are "charged" to the originating group. If the
+ originating group is being throttled you will see the use_delay and delay
+ fields in io.stat increase. The delay value is how many microseconds that are
+ being added to any process that runs in this group. Because this number can
+ grow quite large if there is a lot of swapping or metadata IO occurring we
+ limit the individual delay events to 1 second at a time.
+
+Once the victimized group starts meeting its latency target again it will start
+unthrottling any peer groups that were throttled previously. If the victimized
+group simply stops doing IO the global counter will unthrottle appropriately.
+
+IO Latency Interface Files
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+ io.latency
+ This takes a similar format as the other controllers.
+
+ "MAJOR:MINOR target=<target time in microseconds"
+
+ io.stat
+ If the controller is enabled you will see extra stats in io.stat in
+ addition to the normal ones.
+
+ depth
+ This is the current queue depth for the group.
+
+ avg_lat
+ This is an exponential moving average with a decay rate of 1/exp
+ bound by the sampling interval. The decay rate interval can be
+ calculated by multiplying the win value in io.stat by the
+ corresponding number of samples based on the win value.
+
+ win
+ The sampling window size in milliseconds. This is the minimum
+ duration of time between evaluation events. Windows only elapse
+ with IO activity. Idle periods extend the most recent window.
+
PID
---
diff --git a/Documentation/block/null_blk.txt b/Documentation/block/null_blk.txt
index 07f147381f32..ea2dafe49ae8 100644
--- a/Documentation/block/null_blk.txt
+++ b/Documentation/block/null_blk.txt
@@ -85,3 +85,10 @@ shared_tags=[0/1]: Default: 0
0: Tag set is not shared.
1: Tag set shared between devices for blk-mq. Only makes sense with
nr_devices > 1, otherwise there's no tag set to share.
+
+zoned=[0/1]: Default: 0
+ 0: Block device is exposed as a random-access block device.
+ 1: Block device is exposed as a host-managed zoned block device.
+
+zone_size=[MB]: Default: 256
+ Per zone size when exposed as a zoned block device. Must be a power of two.
diff --git a/Documentation/block/stat.txt b/Documentation/block/stat.txt
index 0dbc946de2ea..0aace9cc536c 100644
--- a/Documentation/block/stat.txt
+++ b/Documentation/block/stat.txt
@@ -31,28 +31,32 @@ write ticks milliseconds total wait time for write requests
in_flight requests number of I/Os currently in flight
io_ticks milliseconds total time this block device has been active
time_in_queue milliseconds total wait time for all requests
+discard I/Os requests number of discard I/Os processed
+discard merges requests number of discard I/Os merged with in-queue I/O
+discard sectors sectors number of sectors discarded
+discard ticks milliseconds total wait time for discard requests
-read I/Os, write I/Os
-=====================
+read I/Os, write I/Os, discard I/0s
+===================================
These values increment when an I/O request completes.
-read merges, write merges
-=========================
+read merges, write merges, discard merges
+=========================================
These values increment when an I/O request is merged with an
already-queued I/O request.
-read sectors, write sectors
-===========================
+read sectors, write sectors, discard_sectors
+============================================
-These values count the number of sectors read from or written to this
-block device. The "sectors" in question are the standard UNIX 512-byte
-sectors, not any device- or filesystem-specific block size. The
-counters are incremented when the I/O completes.
+These values count the number of sectors read from, written to, or
+discarded from this block device. The "sectors" in question are the
+standard UNIX 512-byte sectors, not any device- or filesystem-specific
+block size. The counters are incremented when the I/O completes.
-read ticks, write ticks
-=======================
+read ticks, write ticks, discard ticks
+======================================
These values count the number of milliseconds that I/O requests have
waited on this block device. If there are multiple I/O requests waiting,
diff --git a/Documentation/iostats.txt b/Documentation/iostats.txt
index 04d394a2e06c..49df45f90e8a 100644
--- a/Documentation/iostats.txt
+++ b/Documentation/iostats.txt
@@ -31,6 +31,9 @@ Here are examples of these different formats::
3 0 hda 446216 784926 9550688 4382310 424847 312726 5922052 19310380 0 3376340 23705160
3 1 hda1 35486 38030 38030 38030
+ 4.18+ diskstats:
+ 3 0 hda 446216 784926 9550688 4382310 424847 312726 5922052 19310380 0 3376340 23705160 0 0 0 0
+
On 2.4 you might execute ``grep 'hda ' /proc/partitions``. On 2.6+, you have
a choice of ``cat /sys/block/hda/stat`` or ``grep 'hda ' /proc/diskstats``.
@@ -101,6 +104,18 @@ Field 11 -- weighted # of milliseconds spent doing I/Os
last update of this field. This can provide an easy measure of both
I/O completion time and the backlog that may be accumulating.
+Field 12 -- # of discards completed
+ This is the total number of discards completed successfully.
+
+Field 13 -- # of discards merged
+ See the description of field 2
+
+Field 14 -- # of sectors discarded
+ This is the total number of sectors discarded successfully.
+
+Field 15 -- # of milliseconds spent discarding
+ This is the total number of milliseconds spent by all discards (as
+ measured from __make_request() to end_that_request_last()).
To avoid introducing performance bottlenecks, no locks are held while
modifying these counters. This implies that minor inaccuracies may be