1. 22 Nov, 2016 7 commits
  2. 21 Nov, 2016 3 commits
  3. 18 Nov, 2016 3 commits
  4. 17 Nov, 2016 7 commits
  5. 16 Nov, 2016 3 commits
  6. 15 Nov, 2016 2 commits
  7. 14 Nov, 2016 3 commits
  8. 11 Nov, 2016 6 commits
  9. 10 Nov, 2016 6 commits
    • Jens Axboe's avatar
      block: hook up writeback throttling · 87760e5e
      Jens Axboe authored
      Enable throttling of buffered writeback to make it a lot
      more smooth, and has way less impact on other system activity.
      Background writeback should be, by definition, background
      activity. The fact that we flush huge bundles of it at the time
      means that it potentially has heavy impacts on foreground workloads,
      which isn't ideal. We can't easily limit the sizes of writes that
      we do, since that would impact file system layout in the presence
      of delayed allocation. So just throttle back buffered writeback,
      unless someone is waiting for it.
      
      The algorithm for when to throttle takes its inspiration in the
      CoDel networking scheduling algorithm. Like CoDel, blk-wb monitors
      the minimum latencies of requests over a window of time. In that
      window of time, if the minimum latency of any request exceeds a
      given target, then a scale count is incremented and the queue depth
      is shrunk. The next monitoring window is shrunk accordingly. Unlike
      CoDel, if we hit a window that exhibits good behavior, then we
      simply increment the scale count and re-calculate the limits for that
      scale value. This prevents us from oscillating between a
      close-to-ideal value and max all the time, instead remaining in the
      windows where we get good behavior.
      
      Unlike CoDel, blk-wb allows the scale count to to negative. This
      happens if we primarily have writes going on. Unlike positive
      scale counts, this doesn't change the size of the monitoring window.
      When the heavy writers finish, blk-bw quickly snaps back to it's
      stable state of a zero scale count.
      
      The patch registers a sysfs entry, 'wb_lat_usec'. This sets the latency
      target to me met. It defaults to 2 msec for non-rotational storage, and
      75 msec for rotational storage. Setting this value to '0' disables
      blk-wb. Generally, a user would not have to touch this setting.
      
      We don't enable WBT on devices that are managed with CFQ, and have
      a non-root block cgroup attached. If we have a proportional share setup
      on this particular disk, then the wbt throttling will interfere with
      that. We don't have a strong need for wbt for that case, since we will
      rely on CFQ doing that for us.
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      87760e5e
    • Jens Axboe's avatar
      blk-wbt: add general throttling mechanism · e34cbd30
      Jens Axboe authored
      We can hook this up to the block layer, to help throttle buffered
      writes.
      
      wbt registers a few trace points that can be used to track what is
      happening in the system:
      
      wbt_lat: 259:0: latency 2446318
      wbt_stat: 259:0: rmean=2446318, rmin=2446318, rmax=2446318, rsamples=1,
                     wmean=518866, wmin=15522, wmax=5330353, wsamples=57
      wbt_step: 259:0: step down: step=1, window=72727272, background=8, normal=16, max=32
      
      This shows a sync issue event (wbt_lat) that exceeded it's time. wbt_stat
      dumps the current read/write stats for that window, and wbt_step shows a
      step down event where we now scale back writes. Each trace includes the
      device, 259:0 in this case.
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      e34cbd30
    • Jens Axboe's avatar
      block: add scalable completion tracking of requests · cf43e6be
      Jens Axboe authored
      For legacy block, we simply track them in the request queue. For
      blk-mq, we track them on a per-sw queue basis, which we can then
      sum up through the hardware queues and finally to a per device
      state.
      
      The stats are tracked in, roughly, 0.1s interval windows.
      
      Add sysfs files to display the stats.
      
      The feature is off by default, to avoid any extra overhead. In-kernel
      users of it can turn it on by setting QUEUE_FLAG_STATS in the queue
      flags. We currently don't turn it on if someone just reads any of
      the stats files, that is something we could add as well.
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      cf43e6be
    • Tejun Heo's avatar
      block: cfq_cpd_alloc() should use @gfp · ebc4ff66
      Tejun Heo authored
      cfq_cpd_alloc() which is the cpd_alloc_fn implementation for cfq was
      incorrectly hard coding GFP_KERNEL instead of using the mask specified
      through the @gfp parameter.  This currently doesn't cause any actual
      issues because all current callers specify GFP_KERNEL.  Fix it.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Reported-by: default avatarDan Carpenter <dan.carpenter@oracle.com>
      Fixes: e4a9bde9 ("blkcg: replace blkcg_policy->cpd_size with ->cpd_alloc/free_fn() methods")
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      ebc4ff66
    • Christoph Hellwig's avatar
      nvme: don't pass the full CQE to nvme_complete_async_event · 7bf58533
      Christoph Hellwig authored
      We only need the status and result fields, and passing them explicitly
      makes life a lot easier for the Fibre Channel transport which doesn't
      have a full CQE for the fast path case.
      Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
      Reviewed-by: default avatarKeith Busch <keith.busch@intel.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      7bf58533
    • Christoph Hellwig's avatar
      nvme: introduce struct nvme_request · d49187e9
      Christoph Hellwig authored
      This adds a shared per-request structure for all NVMe I/O.  This structure
      is embedded as the first member in all NVMe transport drivers request
      private data and allows to implement common functionality between the
      drivers.
      
      The first use is to replace the current abuse of the SCSI command
      passthrough fields in struct request for the NVMe command passthrough,
      but it will grow a field more fields to allow implementing things
      like common abort handlers in the future.
      
      The passthrough commands are handled by having a pointer to the SQE
      (struct nvme_command) in struct nvme_request, and the union of the
      possible result fields, which had to be turned from an anonymous
      into a named union for that purpose.  This avoids having to pass
      a reference to a full CQE around and thus makes checking the result
      a lot more lightweight.
      Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
      Reviewed-by: default avatarKeith Busch <keith.busch@intel.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      d49187e9