• Linus Torvalds's avatar
    Merge tag 'io_uring-2019-03-06' of git://git.kernel.dk/linux-block · 38e7571c
    Linus Torvalds authored
    Pull io_uring IO interface from Jens Axboe:
     "Second attempt at adding the io_uring interface.
    
      Since the first one, we've added basic unit testing of the three
      system calls, that resides in liburing like the other unit tests that
      we have so far. It'll take a while to get full coverage of it, but
      we're working towards it. I've also added two basic test programs to
      tools/io_uring. One uses the raw interface and has support for all the
      various features that io_uring supports outside of standard IO, like
      fixed files, fixed IO buffers, and polled IO. The other uses the
      liburing API, and is a simplified version of cp(1).
    
      This adds support for a new IO interface, io_uring.
    
      io_uring allows an application to communicate with the kernel through
      two rings, the submission queue (SQ) and completion queue (CQ) ring.
      This allows for very efficient handling of IOs, see the v5 posting for
      some basic numbers:
    
        https://lore.kernel.org/linux-block/20190116175003.17880-1-axboe@kernel.dk/
    
      Outside of just efficiency, the interface is also flexible and
      extendable, and allows for future use cases like the upcoming NVMe
      key-value store API, networked IO, and so on. It also supports async
      buffered IO, something that we've always failed to support in the
      kernel.
    
      Outside of basic IO features, it supports async polled IO as well.
      This particular feature has already been tested at Facebook months ago
      for flash storage boxes, with 25-33% improvements. It makes polled IO
      actually useful for real world use cases, where even basic flash sees
      a nice win in terms of efficiency, latency, and performance. These
      boxes were IOPS bound before, now they are not.
    
      This series adds three new system calls. One for setting up an
      io_uring instance (io_uring_setup(2)), one for submitting/completing
      IO (io_uring_enter(2)), and one for aux functions like registrating
      file sets, buffers, etc (io_uring_register(2)). Through the help of
      Arnd, I've coordinated the syscall numbers so merge on that front
      should be painless.
    
      Jon did a writeup of the interface a while back, which (except for
      minor details that have been tweaked) is still accurate. Find that
      here:
    
        https://lwn.net/Articles/776703/
    
      Huge thanks to Al Viro for helping getting the reference cycle code
      correct, and to Jann Horn for his extensive reviews focused on both
      security and bugs in general.
    
      There's a userspace library that provides basic functionality for
      applications that don't need or want to care about how to fiddle with
      the rings directly. It has helpers to allow applications to easily set
      up an io_uring instance, and submit/complete IO through it without
      knowing about the intricacies of the rings. It also includes man pages
      (thanks to Jeff Moyer), and will continue to grow support helper
      functions and features as time progresses. Find it here:
    
        git://git.kernel.dk/liburing
    
      Fio has full support for the raw interface, both in the form of an IO
      engine (io_uring), but also with a small test application (t/io_uring)
      that can exercise and benchmark the interface"
    
    * tag 'io_uring-2019-03-06' of git://git.kernel.dk/linux-block:
      io_uring: add a few test tools
      io_uring: allow workqueue item to handle multiple buffered requests
      io_uring: add support for IORING_OP_POLL
      io_uring: add io_kiocb ref count
      io_uring: add submission polling
      io_uring: add file set registration
      net: split out functions related to registering inflight socket files
      io_uring: add support for pre-mapped user IO buffers
      block: implement bio helper to add iter bvec pages to bio
      io_uring: batch io_kiocb allocation
      io_uring: use fget/fput_many() for file references
      fs: add fget_many() and fput_many()
      io_uring: support for IO polling
      io_uring: add fsync support
      Add io_uring IO interface
    38e7571c