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  1. 29 10月, 2013 1 次提交
    • C
      blk-mq: fix for flush deadlock · 3228f48b
      由 Christoph Hellwig 提交于 
      The flush state machine takes in a struct request, which then is
submitted multiple times to the underling driver.  The old block code
requeses the same request for each of those, so it does not have an
issue with tapping into the request pool.  The new one on the other hand
allocates a new request for each of the actualy steps of the flush
sequence. If have already allocated all of the tags for IO, we will
fail allocating the flush request.

Set aside a reserved request just for flushes.
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      3228f48b
  3. 25 10月, 2013 11 次提交
    • C
      blk-mq: add blk_mq_stop_hw_queues · 280d45f6
      由 Christoph Hellwig 提交于 
      Add a helper to iterate over all hw queues and stop them.  This is useful
for driver that implement PM suspend functionality.
Signed-off-by: NChristoph Hellwig <hch@lst.de>

Modified to just call blk_mq_stop_hw_queue() by Jens.
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      280d45f6
    • J
      null_blk: multi queue aware block test driver · f2298c04
      由 Jens Axboe 提交于 
      A driver that simply completes IO it receives, it does no
transfers. Written to fascilitate testing of the blk-mq code.
It supports various module options to use either bio queueing,
rq queueing, or mq mode.
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      f2298c04
    • J
      blk-mq: new multi-queue block IO queueing mechanism · 320ae51f
      由 Jens Axboe 提交于 
      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: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      320ae51f
    • S
      percpu_ida: add an API to return free tags · 1dddc01a
      由 Shaohua Li 提交于 
      Add an API to return free tags, blk-mq-tag will use it.

Note, this just returns a snapshot of free tags number. blk-mq-tag has
two usages of it. One is for info output for diagnosis. The other is to
quickly check if there are free tags for request dispatch checking.
Neither requires very precise.

Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NShaohua Li <shli@fusionio.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      1dddc01a
    • S
      percpu_ida: add percpu_ida_for_each_free · 7fc2ba17
      由 Shaohua Li 提交于 
      Add a new API to iterate free ids. blk-mq-tag will use it.

Note, this doesn't guarantee to iterate all free ids restrictly. Caller
should be aware of this. blk-mq uses it to do sanity check for request
timedout, so can tolerate the limitation.

Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NShaohua Li <shli@fusionio.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      7fc2ba17
    • S
      percpu_ida: make percpu_ida percpu size/batch configurable · e26b53d0
      由 Shaohua Li 提交于 
      Make percpu_ida percpu size/batch configurable. The block-mq-tag will
use it.

After block-mq uses percpu_ida to manage tags, performance is improved.
My test is done in a 2 sockets machine, 12 process cross the 2 sockets.
So if there is lock contention or ipi, should be stressed heavily.
Testing is done for null-blk.

hw_queue_depth	nopatch iops	patch iops
64		~800k/s		~1470k/s
2048		~4470k/s	~4340k/s

Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NShaohua Li <shli@fusionio.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      e26b53d0
    • S
      percpu_counter: make APIs irq safe · 098faf58
      由 Shaohua Li 提交于 
      In my usage, sometimes the percpu APIs are called with irq locked,
sometimes not. lockdep complains there is potential deadlock. Let's
always use percpucounter lock in irq safe way. There should be no
performance penality, as all those are slow code path.

Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NShaohua Li <shli@fusionio.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      098faf58
    • C
      block: remove request ref_count · 71fe07d0
      由 Christoph Hellwig 提交于 
      This reference count has been around since before git history, but the only
place where it's used is in blk_execute_rq, and ther it is entirely useless
as it is incremented before submitting the request and decremented in the
end_io handler before waking up the submitter thread.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      71fe07d0
    • J
      block: make rq->cmd_flags be 64-bit · 5953316d
      由 Jens Axboe 提交于 
      We have officially run out of flags in a 32-bit space. Extend it
to 64-bit even on 32-bit archs.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      5953316d
    • J
      smp: don't warn about csd->flags having CSD_FLAG_LOCK cleared for !wait · c84a83e2
      由 Jens Axboe 提交于 
      blk-mq reuses the request potentially immediately, since the most
cache hot is always given out first. This means that rq->csd could
be reused between csd->func() being called and csd_unlock() being
called. This isn't a problem, since we never use wait == 1 for
the smp call function. Add CSD_FLAG_WAIT to be able to tell the
difference, retaining the warning for other cases.

Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      c84a83e2
    • J
      smp: export __smp_call_function_single() · e3daab6c
      由 Jens Axboe 提交于 
      The blk-mq core and the blk-mq null driver uses it.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Acked-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      e3daab6c
  5. 14 10月, 2013 10 次提交
  7. 13 10月, 2013 16 次提交
  9. 12 10月, 2013 2 次提交
    • V
      ARC: Ignore ptrace SETREGSET request for synthetic register "stop_pc" · 5b242828
      由 Vineet Gupta 提交于 
      ARCompact TRAP_S insn used for breakpoints, commits before exception is
taken (updating architectural PC). So ptregs->ret contains next-PC and
not the breakpoint PC itself. This is different from other restartable
exceptions such as TLB Miss where ptregs->ret has exact faulting PC.
gdb needs to know exact-PC hence ARC ptrace GETREGSET provides for
@stop_pc which returns ptregs->ret vs. EFA depending on the
situation.

However, writing stop_pc (SETREGSET request), which updates ptregs->ret
doesn't makes sense stop_pc doesn't always correspond to that reg as
described above.

This was not an issue so far since user_regs->ret / user_regs->stop_pc
had same value and both writing to ptregs->ret was OK, needless, but NOT
broken, hence not observed.

With gdb "jump", they diverge, and user_regs->ret updating ptregs is
overwritten immediately with stop_pc, which this patch fixes.
Reported-by: NAnton Kolesov <akolesov@synopsys.com>
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>
      5b242828
    • L
      Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus · 46f37519
      由 Linus Torvalds 提交于 
      Pull MIPS fix from Ralf Baechle:
 "Just one fix.  The stack protector was loading the value of the canary
  instead of its address"

* 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus:
  MIPS: stack protector: Fix per-task canary switch
      46f37519