They really belong in block/, especially now since it's not in
drivers/block/ anymore. Additionally, the get_maintainer script
gets it wrong when in fs/.
Suggested-by: Christoph Hellwig <hch@infradead.org>
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Jens Axboe <axboe@fb.com>
Both nr_cache and nr_tags arn't needed for bitmap tag anymore.
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
The selected tag should be selected at random between 0 and
(depth - 1) with probability 1/depth, instead between 0 and
(depth - 2) with probability 1/(depth - 1).
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
The barrier isn't necessary because both atomic_dec_and_test()
and wake_up() implicate one barrier.
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
The unlock memory barrier need to order access to req in free
path and clearing tag bit, otherwise either request free path
may see a allocated request, or initialized request in allocate
path might be modified by the ongoing free path.
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
We first check if we have inflight IO, then retrieve that
same number again. Usually this isn't that costly since the
chance of having the data dirtied in between is small, but
there's no reason for calling part_in_flight() twice.
Signed-off-by: Jens Axboe <axboe@fb.com>
Commit c6d600c6 opened up a small race where we could attempt to
account IO completion on a request, racing with IO start accounting.
Fix this up by ensuring that we've accounted for IO start before
inserting the request.
Signed-off-by: Jens Axboe <axboe@fb.com>
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>
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>
This allows us to avoid a non-atomic memset over ->atomic_flags as well
as killing lots of duplicate initializations.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
Right now we just pick the first CPU in the mask, but that can
easily overload that one. Add some basic batching and round-robin
all the entries in the mask instead.
Signed-off-by: Jens Axboe <axboe@fb.com>
All blk_iopoll functions use iop for parent iopoll structure except
blk_iopoll_complete.This also fixes one kernel-doc warning.
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Jens Axboe <axboe@fb.com>
We already issue a blktrace requeue event in
__blk_mq_requeue_request(), don't do it from the original caller
as well.
Signed-off-by: Jens Axboe <axboe@fb.com>
Refactor the logic around adding a new bio to a software queue,
so we nest the ctx->lock where we really need it (merge and
insertion) and don't hold it when we don't (init and IO start
accounting).
Signed-off-by: Jens Axboe <axboe@fb.com>
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>
This will be needed for pending changes to the scsi midlayer that now
calls lower level block APIs, as well as any blk-mq driver that wants to
contribute to the random pool.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Jens Axboe <axboe@fb.com>
The blk-mq code is using it's own version of the I/O completion affinity
tunables, which causes a few issues:
- the rq_affinity sysfs file doesn't work for blk-mq devices, even if it
still is present, thus breaking existing tuning setups.
- the rq_affinity = 1 mode, which is the defauly for legacy request based
drivers isn't implemented at all.
- blk-mq drivers don't implement any completion affinity with the default
flag settings.
This patches removes the blk-mq ipi_redirect flag and sysfs file, as well
as the internal BLK_MQ_F_SHOULD_IPI flag and replaces it with code that
respects the queue-wide rq_affinity flags and also implements the
rq_affinity = 1 mode.
This means I/O completion affinity can now only be tuned block-queue wide
instead of per context, which seems more sensible to me anyway.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
Jens Axboe
Ming Lei
Christoph Hellwig
Fabian Frederick
Masanari Iida
Christoph Hellwig