Commit graph

29 commits

Author SHA1 Message Date
Sagi Grimberg
415b806de5 blk-mq-sched: Allocate sched reserved tags as specified in the original queue tagset
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>

Modified by me to also check at driver tag allocation time if the
original request was reserved, so we can be sure to allocate a
properly reserved tag at that point in time, too.

Signed-off-by: Jens Axboe <axboe@fb.com>
2017-03-02 08:56:04 -07:00
Omar Sandoval
d96b37c0af blk-mq: move tags and sched_tags info from sysfs to debugfs
These are very tied to the blk-mq tag implementation, so exposing them
to sysfs isn't a great idea. Move the debugging information to debugfs
and add basic entries for the number of tags and the number of reserved
tags to sysfs.

Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2017-01-27 08:17:44 -07:00
Jens Axboe
70f36b6001 blk-mq: allow resize of scheduler requests
Add support for growing the tags associated with a hardware queue, for
the scheduler tags. Currently we only support resizing within the
limits of the original depth, change that so we can grow it as well by
allocating and replacing the existing scheduler tag set.

This is similar to how we could increase the software queue depth with
the legacy IO stack and schedulers.

Signed-off-by: Jens Axboe <axboe@fb.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
2017-01-20 09:05:53 -07:00
Jens Axboe
2af8cbe305 blk-mq: split tag ->rqs[] into two
This is in preparation for having two sets of tags available. For
that we need a static index, and a dynamically assignable one.

Signed-off-by: Jens Axboe <axboe@fb.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
2017-01-17 10:04:15 -07:00
Jens Axboe
4941115bef blk-mq-tag: cleanup the normal/reserved tag allocation
This is in preparation for having another tag set available. Cleanup
the parameters, and allow passing in of tags for blk_mq_put_tag().

Signed-off-by: Jens Axboe <axboe@fb.com>
[hch: even more cleanups]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Omar Sandoval <osandov@fb.com>
2017-01-17 10:03:59 -07:00
Linus Torvalds
12e3d3cdd9 Merge branch 'for-4.9/block-irq' of git://git.kernel.dk/linux-block
Pull blk-mq irq/cpu mapping updates from Jens Axboe:
 "This is the block-irq topic branch for 4.9-rc. It's mostly from
  Christoph, and it allows drivers to specify their own mappings, and
  more importantly, to share the blk-mq mappings with the IRQ affinity
  mappings. It's a good step towards making this work better out of the
  box"

* 'for-4.9/block-irq' of git://git.kernel.dk/linux-block:
  blk_mq: linux/blk-mq.h does not include all the headers it depends on
  blk-mq: kill unused blk_mq_create_mq_map()
  blk-mq: get rid of the cpumask in struct blk_mq_tags
  nvme: remove the post_scan callout
  nvme: switch to use pci_alloc_irq_vectors
  blk-mq: provide a default queue mapping for PCI device
  blk-mq: allow the driver to pass in a queue mapping
  blk-mq: remove ->map_queue
  blk-mq: only allocate a single mq_map per tag_set
  blk-mq: don't redistribute hardware queues on a CPU hotplug event
2016-10-09 17:29:33 -07:00
Omar Sandoval
98d95416db sbitmap: randomize initial alloc_hint values
In order to get good cache behavior from a sbitmap, we want each CPU to
stick to its own cacheline(s) as much as possible. This might happen
naturally as the bitmap gets filled up and the alloc_hint values spread
out, but we really want this behavior from the start. blk-mq apparently
intended to do this, but the code to do this was never wired up. Get rid
of the dead code and make it part of the sbitmap library.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2016-09-17 08:39:14 -06:00
Omar Sandoval
f4a644db86 sbitmap: push alloc policy into sbitmap_queue
Again, there's no point in passing this in every time. Make it part of
struct sbitmap_queue and clean up the API.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2016-09-17 08:39:12 -06:00
Omar Sandoval
40aabb6746 sbitmap: push per-cpu last_tag into sbitmap_queue
Allocating your own per-cpu allocation hint separately makes for an
awkward API. Instead, allocate the per-cpu hint as part of the struct
sbitmap_queue. There's no point for a struct sbitmap_queue without the
cache, but you can still use a bare struct sbitmap.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2016-09-17 08:39:10 -06:00
Omar Sandoval
88459642cb blk-mq: abstract tag allocation out into sbitmap library
This is a generally useful data structure, so make it available to
anyone else who might want to use it. It's also a nice cleanup
separating the allocation logic from the rest of the tag handling logic.

The code is behind a new Kconfig option, CONFIG_SBITMAP, which is only
selected by CONFIG_BLOCK for now.

This should be a complete noop functionality-wise.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2016-09-17 08:38:44 -06:00
Christoph Hellwig
1b157939f9 blk-mq: get rid of the cpumask in struct blk_mq_tags
Unused now that NVMe sets up irq affinity before calling into blk-mq.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2016-09-15 08:42:03 -06:00
Christoph Hellwig
0bf6cd5b95 blk-mq: factor out a helper to iterate all tags for a request_queue
And replace the blk_mq_tag_busy_iter with it - the driver use has been
replaced with a new helper a while ago, and internal to the block we
only need the new version.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
2015-10-01 10:10:57 +02:00
Ming Lei
0048b4837a blk-mq: fix race between timeout and freeing request
Inside timeout handler, blk_mq_tag_to_rq() is called
to retrieve the request from one tag. This way is obviously
wrong because the request can be freed any time and some
fiedds of the request can't be trusted, then kernel oops
might be triggered[1].

Currently wrt. blk_mq_tag_to_rq(), the only special case is
that the flush request can share same tag with the request
cloned from, and the two requests can't be active at the same
time, so this patch fixes the above issue by updating tags->rqs[tag]
with the active request(either flush rq or the request cloned
from) of the tag.

Also blk_mq_tag_to_rq() gets much simplified with this patch.

Given blk_mq_tag_to_rq() is mainly for drivers and the caller must
make sure the request can't be freed, so in bt_for_each() this
helper is replaced with tags->rqs[tag].

[1] kernel oops log
[  439.696220] BUG: unable to handle kernel NULL pointer dereference at 0000000000000158^M
[  439.697162] IP: [<ffffffff812d89ba>] blk_mq_tag_to_rq+0x21/0x6e^M
[  439.700653] PGD 7ef765067 PUD 7ef764067 PMD 0 ^M
[  439.700653] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC ^M
[  439.700653] Dumping ftrace buffer:^M
[  439.700653]    (ftrace buffer empty)^M
[  439.700653] Modules linked in: nbd ipv6 kvm_intel kvm serio_raw^M
[  439.700653] CPU: 6 PID: 2779 Comm: stress-ng-sigfd Not tainted 4.2.0-rc5-next-20150805+ #265^M
[  439.730500] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011^M
[  439.730500] task: ffff880605308000 ti: ffff88060530c000 task.ti: ffff88060530c000^M
[  439.730500] RIP: 0010:[<ffffffff812d89ba>]  [<ffffffff812d89ba>] blk_mq_tag_to_rq+0x21/0x6e^M
[  439.730500] RSP: 0018:ffff880819203da0  EFLAGS: 00010283^M
[  439.730500] RAX: ffff880811b0e000 RBX: ffff8800bb465f00 RCX: 0000000000000002^M
[  439.730500] RDX: 0000000000000000 RSI: 0000000000000202 RDI: 0000000000000000^M
[  439.730500] RBP: ffff880819203db0 R08: 0000000000000002 R09: 0000000000000000^M
[  439.730500] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000202^M
[  439.730500] R13: ffff880814104800 R14: 0000000000000002 R15: ffff880811a2ea00^M
[  439.730500] FS:  00007f165b3f5740(0000) GS:ffff880819200000(0000) knlGS:0000000000000000^M
[  439.730500] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b^M
[  439.730500] CR2: 0000000000000158 CR3: 00000007ef766000 CR4: 00000000000006e0^M
[  439.730500] Stack:^M
[  439.730500]  0000000000000008 ffff8808114eed90 ffff880819203e00 ffffffff812dc104^M
[  439.755663]  ffff880819203e40 ffffffff812d9f5e 0000020000000000 ffff8808114eed80^M
[  439.755663] Call Trace:^M
[  439.755663]  <IRQ> ^M
[  439.755663]  [<ffffffff812dc104>] bt_for_each+0x6e/0xc8^M
[  439.755663]  [<ffffffff812d9f5e>] ? blk_mq_rq_timed_out+0x6a/0x6a^M
[  439.755663]  [<ffffffff812d9f5e>] ? blk_mq_rq_timed_out+0x6a/0x6a^M
[  439.755663]  [<ffffffff812dc1b3>] blk_mq_tag_busy_iter+0x55/0x5e^M
[  439.755663]  [<ffffffff812d88b4>] ? blk_mq_bio_to_request+0x38/0x38^M
[  439.755663]  [<ffffffff812d8911>] blk_mq_rq_timer+0x5d/0xd4^M
[  439.755663]  [<ffffffff810a3e10>] call_timer_fn+0xf7/0x284^M
[  439.755663]  [<ffffffff810a3d1e>] ? call_timer_fn+0x5/0x284^M
[  439.755663]  [<ffffffff812d88b4>] ? blk_mq_bio_to_request+0x38/0x38^M
[  439.755663]  [<ffffffff810a46d6>] run_timer_softirq+0x1ce/0x1f8^M
[  439.755663]  [<ffffffff8104c367>] __do_softirq+0x181/0x3a4^M
[  439.755663]  [<ffffffff8104c76e>] irq_exit+0x40/0x94^M
[  439.755663]  [<ffffffff81031482>] smp_apic_timer_interrupt+0x33/0x3e^M
[  439.755663]  [<ffffffff815559a4>] apic_timer_interrupt+0x84/0x90^M
[  439.755663]  <EOI> ^M
[  439.755663]  [<ffffffff81554350>] ? _raw_spin_unlock_irq+0x32/0x4a^M
[  439.755663]  [<ffffffff8106a98b>] finish_task_switch+0xe0/0x163^M
[  439.755663]  [<ffffffff8106a94d>] ? finish_task_switch+0xa2/0x163^M
[  439.755663]  [<ffffffff81550066>] __schedule+0x469/0x6cd^M
[  439.755663]  [<ffffffff8155039b>] schedule+0x82/0x9a^M
[  439.789267]  [<ffffffff8119b28b>] signalfd_read+0x186/0x49a^M
[  439.790911]  [<ffffffff8106d86a>] ? wake_up_q+0x47/0x47^M
[  439.790911]  [<ffffffff811618c2>] __vfs_read+0x28/0x9f^M
[  439.790911]  [<ffffffff8117a289>] ? __fget_light+0x4d/0x74^M
[  439.790911]  [<ffffffff811620a7>] vfs_read+0x7a/0xc6^M
[  439.790911]  [<ffffffff8116292b>] SyS_read+0x49/0x7f^M
[  439.790911]  [<ffffffff81554c17>] entry_SYSCALL_64_fastpath+0x12/0x6f^M
[  439.790911] Code: 48 89 e5 e8 a9 b8 e7 ff 5d c3 0f 1f 44 00 00 55 89
f2 48 89 e5 41 54 41 89 f4 53 48 8b 47 60 48 8b 1c d0 48 8b 7b 30 48 8b
53 38 <48> 8b 87 58 01 00 00 48 85 c0 75 09 48 8b 97 88 0c 00 00 eb 10
^M
[  439.790911] RIP  [<ffffffff812d89ba>] blk_mq_tag_to_rq+0x21/0x6e^M
[  439.790911]  RSP <ffff880819203da0>^M
[  439.790911] CR2: 0000000000000158^M
[  439.790911] ---[ end trace d40af58949325661 ]---^M

Cc: <stable@vger.kernel.org>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2015-08-15 09:45:21 -06:00
Keith Busch
f26cdc8536 blk-mq: Shared tag enhancements
Storage controllers may expose multiple block devices that share hardware
resources managed by blk-mq. This patch enhances the shared tags so a
low-level driver can access the shared resources not tied to the unshared
h/w contexts. This way the LLD can dynamically add and delete disks and
request queues without having to track all the request_queue hctx's to
iterate outstanding tags.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2015-06-01 14:35:56 -06:00
Shaohua Li
24391c0dc5 blk-mq: add tag allocation policy
This is the blk-mq part to support tag allocation policy. The default
allocation policy isn't changed (though it's not a strict FIFO). The new
policy is round-robin for libata. But it's a try-best implementation. If
multiple tasks are competing, the tags returned will be mixed (which is
unavoidable even with !mq, as requests from different tasks can be
mixed in queue)

Cc: Jens Axboe <axboe@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2015-01-23 14:18:00 -07:00
Jens Axboe
aed3ea94bd block: wake up waiters when a queue is marked dying
If it's dying, we can't expect new request to complete and come
in an wake up other tasks waiting for requests. So after we
have marked it as dying, wake up everybody currently waiting
for a request. Once they wake, they will retry their allocation
and fail appropriately due to the state of the queue.

Tested-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2014-12-31 09:39:16 -07:00
Alexander Gordeev
8537b12034 blk-mq: bitmap tag: fix races on shared ::wake_index fields
Fix racy updates of shared blk_mq_bitmap_tags::wake_index
and blk_mq_hw_ctx::wake_index fields.

Cc: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2014-06-17 22:12:35 -07:00
Ming Lei
cb96a42cc1 blk-mq: fix schedule from atomic context
blk_mq_put_ctx() has to be called before io_schedule() in
bt_get().

This patch fixes the problem by taking similar approach from
percpu_ida allocation for the situation.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2014-06-03 21:04:39 -06:00
Christoph Hellwig
a3bd77567c blk-mq: remove blk_mq_wait_for_tags
The current logic for blocking tag allocation is rather confusing, as we
first allocated and then free again a tag in blk_mq_wait_for_tags, just
to attempt a non-blocking allocation and then repeat if someone else
managed to grab the tag before us.

Instead change blk_mq_alloc_request_pinned to simply do a blocking tag
allocation itself and use the request we get back from it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-28 09:49:23 -06:00
Sam Bradshaw
edf866b380 blk-mq: export blk_mq_tag_busy_iter
Export the blk-mq in-flight tag iterator for driver consumption.
This is particularly useful in exception paths or SRSI where
in-flight IOs need to be cancelled and/or reissued. The NVMe driver
conversion will use this.

Signed-off-by: Sam Bradshaw <sbradshaw@micron.com>
Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-23 13:30:16 -06:00
Jens Axboe
e3a2b3f931 blk-mq: allow changing of queue depth through sysfs
For request_fn based devices, the block layer exports a 'nr_requests'
file through sysfs to allow adjusting of queue depth on the fly.
Currently this returns -EINVAL for blk-mq, since it's not wired up.
Wire this up for blk-mq, so that it now also always dynamic
adjustments of the allowed queue depth for any given block device
managed by blk-mq.

Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-20 11:49:02 -06:00
Jens Axboe
39a9f97e5e Merge branch 'for-3.16/blk-mq-tagging' into for-3.16/core
Signed-off-by: Jens Axboe <axboe@fb.com>

Conflicts:
	block/blk-mq-tag.c
2014-05-19 11:52:35 -06:00
Jens Axboe
e93ecf602b blk-mq: move the cache friendly bitmap type of out blk-mq-tag
We will use it for the pending list in blk-mq core as well.

Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-19 11:02:47 -06:00
Jens Axboe
0d2602ca30 blk-mq: improve support for shared tags maps
This adds support for active queue tracking, meaning that the
blk-mq tagging maintains a count of active users of a tag set.
This allows us to maintain a notion of fairness between users,
so that we can distribute the tag depth evenly without starving
some users while allowing others to try unfair deep queues.

If sharing of a tag set is detected, each hardware queue will
track the depth of its own queue. And if this exceeds the total
depth divided by the number of active queues, the user is actively
throttled down.

The active queue count is done lazily to avoid bouncing that data
between submitter and completer. Each hardware queue gets marked
active when it allocates its first tag, and gets marked inactive
when 1) the last tag is cleared, and 2) the queue timeout grace
period has passed.

Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-13 15:10:52 -06:00
Jens Axboe
59d13bf5f5 blk-mq: use sparser tag layout for lower queue depth
For best performance, spreading tags over multiple cachelines
makes the tagging more efficient on multicore systems. But since
we have 8 * sizeof(unsigned long) tags per cacheline, we don't
always get a nice spread.

Attempt to spread the tags over at least 4 cachelines, using fewer
number of bits per unsigned long if we have to. This improves
tagging performance in setups with 32-128 tags. For higher depths,
the spread is the same as before (BITS_PER_LONG tags per cacheline).

Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-09 13:41:15 -06:00
Jens Axboe
4bb659b156 blk-mq: implement new and more efficient tagging scheme
blk-mq currently uses percpu_ida for tag allocation. But that only
works well if the ratio between tag space and number of CPUs is
sufficiently high. For most devices and systems, that is not the
case. The end result if that we either only utilize the tag space
partially, or we end up attempting to fully exhaust it and run
into lots of lock contention with stealing between CPUs. This is
not optimal.

This new tagging scheme is a hybrid bitmap allocator. It uses
two tricks to both be SMP friendly and allow full exhaustion
of the space:

1) We cache the last allocated (or freed) tag on a per blk-mq
   software context basis. This allows us to limit the space
   we have to search. The key element here is not caching it
   in the shared tag structure, otherwise we end up dirtying
   more shared cache lines on each allocate/free operation.

2) The tag space is split into cache line sized groups, and
   each context will start off randomly in that space. Even up
   to full utilization of the space, this divides the tag users
   efficiently into cache line groups, avoiding dirtying the same
   one both between allocators and between allocator and freeer.

This scheme shows drastically better behaviour, both on small
tag spaces but on large ones as well. It has been tested extensively
to show better performance for all the cases blk-mq cares about.

Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-09 09:36:49 -06:00
Jens Axboe
5810d903fa blk-mq: fix waiting for reserved tags
blk_mq_wait_for_tags() is only able to wait for "normal" tags,
not reserved tags. Pass in which one we should attempt to get
a tag for, so that waiting for reserved tags will work.

Reserved tags are used for internal commands, which are usually
serialized. Hence no waiting generally takes place, but we should
ensure that it actually works if users need that functionality.

Signed-off-by: Jens Axboe <axboe@fb.com>
2014-04-29 20:49:48 -06:00
Christoph Hellwig
24d2f90309 blk-mq: split out tag initialization, support shared tags
Add a new blk_mq_tag_set structure that gets set up before we initialize
the queue.  A single blk_mq_tag_set structure can be shared by multiple
queues.

Signed-off-by: Christoph Hellwig <hch@lst.de>

Modular export of blk_mq_{alloc,free}_tagset added by me.

Signed-off-by: Jens Axboe <axboe@fb.com>
2014-04-15 14:18:02 -06:00
Jens Axboe
320ae51fee blk-mq: new multi-queue block IO queueing mechanism
Linux currently has two models for block devices:

- The classic request_fn based approach, where drivers use struct
  request units for IO. The block layer provides various helper
  functionalities to let drivers share code, things like tag
  management, timeout handling, queueing, etc.

- The "stacked" approach, where a driver squeezes in between the
  block layer and IO submitter. Since this bypasses the IO stack,
  driver generally have to manage everything themselves.

With drivers being written for new high IOPS devices, the classic
request_fn based driver doesn't work well enough. The design dates
back to when both SMP and high IOPS was rare. It has problems with
scaling to bigger machines, and runs into scaling issues even on
smaller machines when you have IOPS in the hundreds of thousands
per device.

The stacked approach is then most often selected as the model
for the driver. But this means that everybody has to re-invent
everything, and along with that we get all the problems again
that the shared approach solved.

This commit introduces blk-mq, block multi queue support. The
design is centered around per-cpu queues for queueing IO, which
then funnel down into x number of hardware submission queues.
We might have a 1:1 mapping between the two, or it might be
an N:M mapping. That all depends on what the hardware supports.

blk-mq provides various helper functions, which include:

- Scalable support for request tagging. Most devices need to
  be able to uniquely identify a request both in the driver and
  to the hardware. The tagging uses per-cpu caches for freed
  tags, to enable cache hot reuse.

- Timeout handling without tracking request on a per-device
  basis. Basically the driver should be able to get a notification,
  if a request happens to fail.

- Optional support for non 1:1 mappings between issue and
  submission queues. blk-mq can redirect IO completions to the
  desired location.

- Support for per-request payloads. Drivers almost always need
  to associate a request structure with some driver private
  command structure. Drivers can tell blk-mq this at init time,
  and then any request handed to the driver will have the
  required size of memory associated with it.

- Support for merging of IO, and plugging. The stacked model
  gets neither of these. Even for high IOPS devices, merging
  sequential IO reduces per-command overhead and thus
  increases bandwidth.

For now, this is provided as a potential 3rd queueing model, with
the hope being that, as it matures, it can replace both the classic
and stacked model. That would get us back to having just 1 real
model for block devices, leaving the stacked approach to dm/md
devices (as it was originally intended).

Contributions in this patch from the following people:

Shaohua Li <shli@fusionio.com>
Alexander Gordeev <agordeev@redhat.com>
Christoph Hellwig <hch@infradead.org>
Mike Christie <michaelc@cs.wisc.edu>
Matias Bjorling <m@bjorling.me>
Jeff Moyer <jmoyer@redhat.com>

Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2013-10-25 11:56:00 +01:00