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  1. 21 Apr, 2017 4 commits
    • Helen Koike's avatar
      nvme: improve performance for virtual NVMe devices · f9f38e33
      Helen Koike authored 
      This change provides a mechanism to reduce the number of MMIO doorbell
writes for the NVMe driver. When running in a virtualized environment
like QEMU, the cost of an MMIO is quite hefy here. The main idea for
the patch is provide the device two memory location locations:
 1) to store the doorbell values so they can be lookup without the doorbell
    MMIO write
 2) to store an event index.
I believe the doorbell value is obvious, the event index not so much.
Similar to the virtio specification, the virtual device can tell the
driver (guest OS) not to write MMIO unless you are writing past this
value.

FYI: doorbell values are written by the nvme driver (guest OS) and the
event index is written by the virtual device (host OS).

The patch implements a new admin command that will communicate where
these two memory locations reside. If the command fails, the nvme
driver will work as before without any optimizations.

Contributions:
  Eric Northup <digitaleric@google.com>
  Frank Swiderski <fes@google.com>
  Ted Tso <tytso@mit.edu>
  Keith Busch <keith.busch@intel.com>

Just to give an idea on the performance boost with the vendor
extension: Running fio [1], a stock NVMe driver I get about 200K read
IOPs with my vendor patch I get about 1000K read IOPs. This was
running with a null device i.e. the backing device simply returned
success on every read IO request.

[1] Running on a 4 core machine:
  fio --time_based --name=benchmark --runtime=30
  --filename=/dev/nvme0n1 --nrfiles=1 --ioengine=libaio --iodepth=32
  --direct=1 --invalidate=1 --verify=0 --verify_fatal=0 --numjobs=4
  --rw=randread --blocksize=4k --randrepeat=false
Signed-off-by: default avatarRob Nelson <rlnelson@google.com>
[mlin: port for upstream]
Signed-off-by: default avatarMing Lin <mlin@kernel.org>
[koike: updated for upstream]
Signed-off-by: default avatarHelen Koike <helen.koike@collabora.co.uk>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarKeith Busch <keith.busch@intel.com>
      f9f38e33
    • Keith Busch's avatar
      nvme/pci: Don't set reserved SQ create flags · 81c1cd98
      Keith Busch authored 
      The QPRIO field is only valid if weighted round robin arbitration is used,
and this driver doesn't enable that controller configuration option.
Signed-off-by: default avatarKeith Busch <keith.busch@intel.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarSagi Grimberg <sagi@grimberg.me>
      81c1cd98
    • Jens Axboe's avatar
      blk-stat: kill blk_stat_rq_ddir() · 99c749a4
      Jens Axboe authored 
      No point in providing and exporting this helper. There's just
one (real) user of it, just use rq_data_dir().
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      99c749a4
    • Josef Bacik's avatar
      nbd: set the max segments to USHRT_MAX · 1cc1f17a
      Josef Bacik authored 
      I lack the basic understanding of what segments mean, so we were being
limited to 512kib requests even with higher max_sectors sizes set.
Setting the maximum number of segments to unlimited allows us to
actually have arbitrarily large IO's go through NBD.
Signed-off-by: default avatarJosef Bacik <jbacik@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      1cc1f17a
  3. 20 Apr, 2017 36 commits
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